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50 React interview questions that must be met

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March 24, 2019

50 React interview questions that must be met

If you are an aspiring front-end programmer and are ready to interview, this article is for you. This article is the perfect guide to what you need to learn and interview React.

JavaScript tools are slowly and steadily rooted in the market, and demand for React is growing exponentially. Choosing the right technology to develop an application or website is becoming more and more challenging. React is considered to be the fastest growing Javascript framework.

As of today, there are about 1,000 contributors on Github. Unique features such as Virtual DOM and reusable components attract the attention of front-end developers. Although it is just a library of “views” in MVC (Model-View-Controller), it also poses a strong challenge to a comprehensive framework such as Angular, Meteor, Vue. The following picture shows the trend of the popular JS framework:

React interview questions

Here are the 50 React interview questions and answers that the interviewer is most likely to ask . For your convenience, I have classified them:

basic knowledge
React component
React Redux
React routing

basic knowledge

1. Distinguish between Real DOM and Virtual DOM

Real DOM	Virtual DOM
1. The update is slow.	1. Updates are faster.
2. You can update the HTML directly.	2. It is not possible to update the HTML directly.
3. If the element is updated, create a new DOM.	3. Update the JSX if the element is updated.
4. DOM operations are costly.	4. DOM operations are very simple.
5. More memory is consumed.	5. Very little memory consumption.

2. What is React?

React is the front-end JavaScript library that Facebook developed in 2011.
It follows a component-based approach that helps build reusable UI components.
It is used to develop complex and interactive web and mobile UIs.
Although it was only open source in 2015, there is a large support community.

3. What are the characteristics of React?

The main features of React are as follows:

It uses a virtual DOM instead of a real DOM.
It can be rendered on the server side .
It follows a one-way data flow or data binding.

4. List some of the key benefits of React.

Some of the main advantages of React are:

It improves the performance of the application
Can be easily used on the client and server side
The code is very readable due to JSX
React is easy to integrate with other frameworks such as Meteor, Angular
Using React, writing UI test cases is very easy

5. What are the limitations of React?

The limitations of React are as follows:

React is just a library, not a complete framework
Its library is very large and takes time to understand
Novice programmers may have a hard time understanding
Encoding becomes complicated because it uses inline templates and JSX

6. What is JSX?

JSX is short for JavaScript XML. Is a file used by React that takes advantage of JavaScript’s expressiveness and HTML-like template syntax. This makes the HTML file very easy to understand. This file makes the application very reliable and can improve its performance. The following is an example of JSX:

Render(){
Return (
<div>
<h1> Hello World from Edureka!!</h1>
</div>
);
}

7. Do you know Virtual DOM? Explain how it works.

Virtual DOM is a lightweight JavaScript object that was originally just a copy of the real DOM. It is a node tree that takes elements, their properties, and content as objects and their properties. React’s rendering function creates a node tree from the React component. It then updates the tree in response to changes in the data model that are caused by various actions performed by the user or the system.

The Virtual DOM work process has three simple steps.

1. Whenever the underlying data changes, the entire UI will be re-rendered in the Virtual DOM description.

2. Then calculate the difference between the previous DOM representation and the new representation.

3. Once the calculation is complete, the real DOM will only be updated with the actual changes.

8. Why can’t the browser read JSX?

Browsers can only process JavaScript objects, not JSX in regular JavaScript objects. So in order for the browser to be able to read JSX, first, you need to convert the JSX file to a JavaScript object with a JSX converter like Babel and then pass it to the browser.

9. What is the difference in React’s ES6 syntax compared to ES5?

The following syntax is the difference between ES5 and ES6:

1.require and import

// ES5
Var React = require( ‘react’ );
// ES6
Import React from ‘react’ ;

2.export and exports

// ES5
Module.exports = Component;
// ES6
Export default Component;

3.component and function

// ES5
Var MyComponent = React.createClass({
Render: function () {
Return
<h3>Hello Edureka!</h3>;
}
});
// ES6
Class MyComponent extends React.Component {
Render() {
Return
<h3>Hello Edureka!</h3>;
}
}

4.props

// ES5
Var App = React.createClass({
propTypes: { name : React.PropTypes.string },
Render: function () {
Return
<h3>Hello, {this.props. name }!</h3>;
}
});
// ES6
Class App extends React.Component {
Render() {
Return
<h3>Hello, {this.props. name }!</h3>;
}
}

5.state

// ES5
Var App = React.createClass({
getInitialState: function () {
Return { name : ‘world’ };
},
Render: function () {
Return
<h3>Hello, {this.state. name }!</h3>;
}
});
// ES6
Class App extends React.Component {
Constructor() {
Super();
This.state = { name : ‘world’ };
}
Render() {
Return
<h3>Hello, {this.state. name }!</h3>;
}
}

10. What is the difference between React and Angular?

theme	React	Angular
1. Architecture	Only View in MVC	Complete MVC
2. Rendering	Can perform server-side rendering	Client rendering
3. DOM	Use virtual DOM	Use real DOM
4. Data binding	One-way data binding	Two-way data binding
5. Debugging	Compile time debugging	Runtime debugging
6. Author	Facebook	Google

React component

11. How do you understand the phrase “everything is a component in React”.

A component is a building block of the React application UI. These components divide the entire UI into small, independent and reusable parts. Each component is independent of each other and does not affect the rest of the UI.

12. How to explain the purpose of render() in React.

Each React component is required to have a render() . It returns a React element that is a representation of the native DOM component. If you need to render multiple HTML elements, you must combine them in a closed tag, such as <form>, <group>, , <div>and so on. This function must be kept pure, that is, it must return the same result every time it is called.

13. How do you embed two or more components into one component?

You can embed components into one component in the following ways:

Class MyComponent extends React.Component{
Render(){
Return (
<div>
<h1>Hello</h1>
<Header/>
</div>
);
}
}
Class Header extends React.Component{
Render(){
Return
<h1>Header Component</h1>
};
}
ReactDOM.render(
<MyComponent/>, document.getElementById( ‘content’ )
);

14. What is Props?

Props is short for attributes in React. They are read-only components and must be kept pure, ie immutable. They are always passed from the parent component to the child component throughout the application. Subcomponents can never send prop back to the parent component. This helps maintain one-way data streams and is typically used to render dynamically generated data.

15. What is the status in React? How is it used?

The state is at the heart of the React component and is the source of the data and must be as simple as possible. Basically, a state is an object that determines the presentation and behavior of a component. Unlike props, they are mutable and create dynamic and interactive components. You can this.state()access them.

16. Distinguish between state and props

condition	State	Props
1. Receive initial values from the parent component	Yes	Yes
2. The parent component can change the value	No	Yes
3. Set default values in the component	Yes	Yes
4. Internal changes in components	Yes	No
5. Set the initial value of the subcomponent	Yes	Yes
6. Change inside the subcomponent	No	Yes

17. How do I update the status of a component?

You can this.setState()update component.

Class MyComponent extends React.Component {
Constructor() {
Super();
This.state = {
name : ‘Maxx’ ,
Id: ‘101’
}
}
Render()
{
setTimeout(()=>{ this.setState ({ name : ‘Jaeha’ , id: ‘222’ })}, 2000)
Return (
<div>
<h1>Hello {this.state. name }</h1>
<h2>Your Id is {this.state.id}</h2>
</div>
);
}
}
ReactDOM.render(
<MyComponent/>, document.getElementById( ‘content’ )
);

18. What is the arrow function in React? how to use?

The arrow function ( => ) is a short phrase used to write function expressions. These functions allow the context of the component to be properly bound, because automatic binding cannot be used by default in ES6. The arrow function is very useful when using higher order functions.

//General way
Render() {
Return (
<MyInput onChange = {this.handleChange.bind(this) } />
);
}
// With Arrow Function
Render() {
Return (
<MyInput onChange = { (e)=>this.handleOnChange(e) } />
);
}

19. Distinguish between stateful and stateless components.

Stateful component	Stateless component
1. Store information about component state changes in memory	1. Calculate the internal state of the component
2. Have the right to change the status	2. No right to change state
3. Contains possible past, present and future state changes	3. Does not include past, present and future state changes that may occur
4. Accept notifications for stateless component state change requests and then send props to them.	4. Receive props from the stateful component and treat it as a callback function.

20. What is the stage of the React component life cycle?

The life cycle of a React component has three distinct phases:

Initial rendering phase: This is the stage where the component is about to begin its life journey and enter the DOM.
Update phase: Once a component is added to the DOM, it can only be updated and re-rendered when the prop or state changes. These only happen at this stage.
Unload phase: This is the final phase of the component lifecycle, where components are destroyed and removed from the DOM.

21. Explain in detail the lifecycle approach to React components.

Some of the most important life cycle methods are:

componentWillMount () – Executes before rendering, both on the client and server side.
componentDidMount () – executed on the client only after the first rendering.
componentWillReceiveProps () – Called when props is received from the parent class and before another renderer is called.
shouldComponentUpdate () – Returns true or false based on a specific condition. Returns true if you wish to update the componentor falseotherwise. By default it returns false.
componentWillUpdate () – Called before rendering in the DOM.
componentDidUpdate () – Called immediately after the rendering has taken place.
componentWillUnmount () – Called after the component has been unloaded from the DOM. Used to clean up memory space.

22. What is the event in React?

In React, events are triggered responses to specific actions such as mouseovers, mouse clicks, and keys. Handling these events is similar to handling events in DOM elements. But there are some grammatical differences, such as:

Name the event with hump nomenclature instead of just lowercase letters.
Events are passed as functions instead of strings.

The event parameter re-emphasizes a set of event-specific properties. Each event type contains its own properties and behaviors that can only be accessed through its event handler.

23. How do I create an event in React?

Class Display extends React.Component({
Show(evt) {
// code
},
Render() {
// Render the div with an onClick prop (value is a function )
Return (
<div onClick={this.show}>Click Me!</div>
);
}
});

24. What is the synthetic event in React?

A synthetic event is an object that acts as a cross-browser wrapper around a browser’s native event. They combine the behavior of different browsers into one API. This is done to ensure that events display consistent properties in different browsers.

25. What do you know about React’s refs?

Refs is shorthand for references in React. It is a property that helps store references to specific React elements or components, and it will be returned by the component render configuration function. A reference to a specific element or component returned by render(). They come in handy when you need to make DOM measurements or add methods to your components.

Class ReferenceDemo extends React.Component{
Display() {
Const name = this.inputDemo.value;
document.getElementById( ‘disp’ ).innerHTML = name ;
}
Render() {
Return (
<div>
Name : <input type= “text” ref={input => this.inputDemo = input} />
<button name = “Click” onClick={this.display}>Click</button>
<h2>Hello <span id= “disp” ></span> !!!</h2>
</div>
);
}
}

26. List some cases where Refs should be used.

The following is the case where refs should be used:

Need to manage focus, select text or media playback
Triggered animation
Integrate with third-party DOM libraries

27. How to modularize the code in React?

You can use the export and import attributes to modularize your code. They help to write components separately in different files.

//ChildComponent.jsx
Export default class ChildComponent extends React.Component {
Render() {
Return (
<div>
<h1>This is a child component</h1>
</div>
);
}
}
//ParentComponent.jsx
Import ChildComponent from ‘./childcomponent.js’ ;
Class ParentComponent extends React.Component {
Render() {
Return (
<div>
<App />
</div>
);
}
}

28. How to create a form in React

React forms are similar to HTML forms. React However, the state attributes contained in the assembly state, and only through setState()updating. Therefore elements cannot directly update their state, their commits are handled by JavaScript functions. This function provides full access to the data that the user enters into the form.

handleSubmit(event) {
Alert( ‘A name was submitted: ‘ + this.state.value);
event.preventDefault();
}
Render() {
Return (
<form onSubmit={this.handleSubmit}>
<label>
Name :
<input type= “text” value={this.state.value} onChange={this.handleSubmit} />
</label>
<input type= “submit” value= “Submit” />
</form>
);
}

29. How much do you know about controlled and uncontrolled components?

Controlled component	Uncontrolled component
Not maintaining your status	Keep your own state
2. Data is controlled by the parent component	2. Data is controlled by DOM
3. Get the current value via props and then notify the change via a callback	3. Refs is used to get its current value

30. What is a high-level component (HOC)?

High-level components are an advanced method of reusing component logic and are a component pattern derived from React. A HOC is a custom component that contains another component within it. They can accept any dynamics provided by subcomponents, but will not modify or copy any of the behaviors in their input components. You can think of HOC as a “Pure” component.

31. What can you do with HOC?

HOC can be used for many tasks, such as:

Code reuse, logic and boot abstraction
Render hijacking
State abstraction and control
Props control

32. What is a pure component?

The Pure component is the simplest and fastest component that can be written. They can replace any component that only has render() . These components enhance the simplicity of the code and the performance of the application.

33. What is the importance of the key in React?

Key is used to identify the unique Virtual DOM element and its corresponding data for the driver UI. They help React optimize rendering by reclaiming all of the current elements in the DOM. These keys must be unique numbers or strings, and React simply reorders the elements instead of re-rendering them. This can improve the performance of your application.

React Redux

34. What are the main issues of the MVC framework?

Here are some of the main issues with the MVC framework:

Very expensive for DOM operations
The program runs slowly and is inefficient
Serious memory waste
Component models need to be built around models and views due to circular dependencies

50 React interview questions that must be met

If you are an aspiring front-end programmer and are ready to interview, this article is for you. This article is the perfect guide to what you need to learn and interview React.

Author: Crazy house technology Source: segmentfault | 2019-03-23 20:00: Collection

share it

If you are an aspiring front-end programmer and are ready to interview, this article is for you. This article is the perfect guide to what you need to learn and interview React.

JavaScript tools are slowly and steadily rooted in the market, and demand for React is growing exponentially. Choosing the right technology to develop an application or website is becoming more and more challenging. React is considered to be the fastest growing Javascript framework.

As of today, there are about 1,000 contributors on Github. Unique features such as Virtual DOM and reusable components attract the attention of front-end developers. Although it is just a library of “views” in MVC (Model-View-Controller), it also poses a strong challenge to a comprehensive framework such as Angular, Meteor, Vue. The following picture shows the trend of the popular JS framework:

Trends in the JS framework

React interview questions

Here are the 50 React interview questions and answers that the interviewer is most likely to ask . For your convenience, I have classified them:

basic knowledge
React component
React Redux
React routing

basic knowledge

1. Distinguish between Real DOM and Virtual DOM

Real DOM	Virtual DOM
1. The update is slow.	1. Updates are faster.
2. You can update the HTML directly.	2. It is not possible to update the HTML directly.
3. If the element is updated, create a new DOM.	3. Update the JSX if the element is updated.
4. DOM operations are costly.	4. DOM operations are very simple.
5. More memory is consumed.	5. Very little memory consumption.

2. What is React?

React is the front-end JavaScript library that Facebook developed in 2011.
It follows a component-based approach that helps build reusable UI components.
It is used to develop complex and interactive web and mobile UIs.
Although it was only open source in 2015, there is a large support community.

3. What are the characteristics of React?

The main features of React are as follows:

It uses a virtual DOM instead of a real DOM.
It can be rendered on the server side .
It follows a one-way data flow or data binding.

4. List some of the key benefits of React.

Some of the main advantages of React are:

It improves the performance of the application
Can be easily used on the client and server side
The code is very readable due to JSX
React is easy to integrate with other frameworks such as Meteor, Angular
Using React, writing UI test cases is very easy

5. What are the limitations of React?

The limitations of React are as follows:

React is just a library, not a complete framework
Its library is very large and takes time to understand
Novice programmers may have a hard time understanding
Encoding becomes complicated because it uses inline templates and JSX

6. What is JSX?

JSX is short for JavaScript XML. Is a file used by React that takes advantage of JavaScript’s expressiveness and HTML-like template syntax. This makes the HTML file very easy to understand. This file makes the application very reliable and can improve its performance. The following is an example of JSX:

Render(){
Return (
<div>
<h1> Hello World from Edureka!!</h1>
</div>
);
}

7. Do you know Virtual DOM? Explain how it works.

Virtual DOM is a lightweight JavaScript object that was originally just a copy of the real DOM. It is a node tree that takes elements, their properties, and content as objects and their properties. React’s rendering function creates a node tree from the React component. It then updates the tree in response to changes in the data model that are caused by various actions performed by the user or the system.

The Virtual DOM work process has three simple steps.

1. Whenever the underlying data changes, the entire UI will be re-rendered in the Virtual DOM description.

2. Then calculate the difference between the previous DOM representation and the new representation.

3. Once the calculation is complete, the real DOM will only be updated with the actual changes.

8. Why can’t the browser read JSX?

Browsers can only process JavaScript objects, not JSX in regular JavaScript objects. So in order for the browser to be able to read JSX, first, you need to convert the JSX file to a JavaScript object with a JSX converter like Babel and then pass it to the browser.

9. What is the difference in React’s ES6 syntax compared to ES5?

The following syntax is the difference between ES5 and ES6:

1.require and import

// ES5
Var React = require( ‘react’ );
// ES6
Import React from ‘react’ ;

2.export and exports

// ES5
Module.exports = Component;
// ES6
Export default Component;

3.component and function

// ES5
Var MyComponent = React.createClass({
Render: function () {
Return
<h3>Hello Edureka!</h3>;
}
});
// ES6
Class MyComponent extends React.Component {
Render() {
Return
<h3>Hello Edureka!</h3>;
}
}

4.props

// ES5
Var App = React.createClass({
propTypes: { name : React.PropTypes.string },
Render: function () {
Return
<h3>Hello, {this.props. name }!</h3>;
}
});
// ES6
Class App extends React.Component {
Render() {
Return
<h3>Hello, {this.props. name }!</h3>;
}
}

5.state

// ES5
Var App = React.createClass({
getInitialState: function () {
Return { name : ‘world’ };
},
Render: function () {
Return
<h3>Hello, {this.state. name }!</h3>;
}
});
// ES6
Class App extends React.Component {
Constructor() {
Super();
This.state = { name : ‘world’ };
}
Render() {
Return
<h3>Hello, {this.state. name }!</h3>;
}
}

10. What is the difference between React and Angular?

theme	React	Angular
1. Architecture	Only View in MVC	Complete MVC
2. Rendering	Can perform server-side rendering	Client rendering
3. DOM	Use virtual DOM	Use real DOM
4. Data binding	One-way data binding	Two-way data binding
5. Debugging	Compile time debugging	Runtime debugging
6. Author	Facebook	Google

React component

11. How do you understand the phrase “everything is a component in React”.

A component is a building block of the React application UI. These components divide the entire UI into small, independent and reusable parts. Each component is independent of each other and does not affect the rest of the UI.

12. How to explain the purpose of render() in React.

Each React component is required to have a render() . It returns a React element that is a representation of the native DOM component. If you need to render multiple HTML elements, you must combine them in a closed tag, such as <form>, <group>, , <div>and so on. This function must be kept pure, that is, it must return the same result every time it is called.

13. How do you embed two or more components into one component?

You can embed components into one component in the following ways:

Class MyComponent extends React.Component{
Render(){
Return (
<div>
<h1>Hello</h1>
<Header/>
</div>
);
}
}
Class Header extends React.Component{
Render(){
Return
<h1>Header Component</h1>
};
}
ReactDOM.render(
<MyComponent/>, document.getElementById( ‘content’ )
);

14. What is Props?

Props is short for attributes in React. They are read-only components and must be kept pure, ie immutable. They are always passed from the parent component to the child component throughout the application. Subcomponents can never send prop back to the parent component. This helps maintain one-way data streams and is typically used to render dynamically generated data.

15. What is the status in React? How is it used?

The state is at the heart of the React component and is the source of the data and must be as simple as possible. Basically, a state is an object that determines the presentation and behavior of a component. Unlike props, they are mutable and create dynamic and interactive components. You can this.state()access them.

16. Distinguish between state and props

condition	State	Props
1. Receive initial values from the parent component	Yes	Yes
2. The parent component can change the value	No	Yes
3. Set default values in the component	Yes	Yes
4. Internal changes in components	Yes	No
5. Set the initial value of the subcomponent	Yes	Yes
6. Change inside the subcomponent	No	Yes

17. How do I update the status of a component?

You can this.setState()update component.

Class MyComponent extends React.Component {
Constructor() {
Super();
This.state = {
name : ‘Maxx’ ,
Id: ‘101’
}
}
Render()
{
setTimeout(()=>{ this.setState ({ name : ‘Jaeha’ , id: ‘222’ })}, 2000)
Return (
<div>
<h1>Hello {this.state. name }</h1>
<h2>Your Id is {this.state.id}</h2>
</div>
);
}
}
ReactDOM.render(
<MyComponent/>, document.getElementById( ‘content’ )
);

18. What is the arrow function in React? how to use?

The arrow function ( => ) is a short phrase used to write function expressions. These functions allow the context of the component to be properly bound, because automatic binding cannot be used by default in ES6. The arrow function is very useful when using higher order functions.

//General way
Render() {
Return (
<MyInput onChange = {this.handleChange.bind(this) } />
);
}
// With Arrow Function
Render() {
Return (
<MyInput onChange = { (e)=>this.handleOnChange(e) } />
);
}

19. Distinguish between stateful and stateless components.

Stateful component	Stateless component
1. Store information about component state changes in memory	1. Calculate the internal state of the component
2. Have the right to change the status	2. No right to change state
3. Contains possible past, present and future state changes	3. Does not include past, present and future state changes that may occur
4. Accept notifications for stateless component state change requests and then send props to them.	4. Receive props from the stateful component and treat it as a callback function.

20. What is the stage of the React component life cycle?

The life cycle of a React component has three distinct phases:

Initial rendering phase: This is the stage where the component is about to begin its life journey and enter the DOM.
Update phase: Once a component is added to the DOM, it can only be updated and re-rendered when the prop or state changes. These only happen at this stage.
Unload phase: This is the final phase of the component lifecycle, where components are destroyed and removed from the DOM.

21. Explain in detail the lifecycle approach to React components.

Some of the most important life cycle methods are:

componentWillMount () – Executes before rendering, both on the client and server side.
componentDidMount () – executed on the client only after the first rendering.
componentWillReceiveProps () – Called when props is received from the parent class and before another renderer is called.
shouldComponentUpdate () – Returns true or false based on a specific condition. Returns true if you wish to update the componentor falseotherwise. By default it returns false.
componentWillUpdate () – Called before rendering in the DOM.
componentDidUpdate () – Called immediately after the rendering has taken place.
componentWillUnmount () – Called after the component has been unloaded from the DOM. Used to clean up memory space.

22. What is the event in React?

In React, events are triggered responses to specific actions such as mouseovers, mouse clicks, and keys. Handling these events is similar to handling events in DOM elements. But there are some grammatical differences, such as:

Name the event with hump nomenclature instead of just lowercase letters.
Events are passed as functions instead of strings.

The event parameter re-emphasizes a set of event-specific properties. Each event type contains its own properties and behaviors that can only be accessed through its event handler.

23. How do I create an event in React?

Class Display extends React.Component({
Show(evt) {
// code
},
Render() {
// Render the div with an onClick prop (value is a function )
Return (
<div onClick={this.show}>Click Me!</div>
);
}
});

24. What is the synthetic event in React?

A synthetic event is an object that acts as a cross-browser wrapper around a browser’s native event. They combine the behavior of different browsers into one API. This is done to ensure that events display consistent properties in different browsers.

25. What do you know about React’s refs?

Refs is shorthand for references in React. It is a property that helps store references to specific React elements or components, and it will be returned by the component render configuration function. A reference to a specific element or component returned by render(). They come in handy when you need to make DOM measurements or add methods to your components.

Class ReferenceDemo extends React.Component{
Display() {
Const name = this.inputDemo.value;
document.getElementById( ‘disp’ ).innerHTML = name ;
}
Render() {
Return (
<div>
Name : <input type= “text” ref={input => this.inputDemo = input} />
<button name = “Click” onClick={this.display}>Click</button>
<h2>Hello <span id= “disp” ></span> !!!</h2>
</div>
);
}
}

26. List some cases where Refs should be used.

The following is the case where refs should be used:

Need to manage focus, select text or media playback
Triggered animation
Integrate with third-party DOM libraries

27. How to modularize the code in React?

You can use the export and import attributes to modularize your code. They help to write components separately in different files.

//ChildComponent.jsx
Export default class ChildComponent extends React.Component {
Render() {
Return (
<div>
<h1>This is a child component</h1>
</div>
);
}
}
//ParentComponent.jsx
Import ChildComponent from ‘./childcomponent.js’ ;
Class ParentComponent extends React.Component {
Render() {
Return (
<div>
<App />
</div>
);
}
}

28. How to create a form in React

React forms are similar to HTML forms. React However, the state attributes contained in the assembly state, and only through setState()updating. Therefore elements cannot directly update their state, their commits are handled by JavaScript functions. This function provides full access to the data that the user enters into the form.

handleSubmit(event) {
Alert( ‘A name was submitted: ‘ + this.state.value);
event.preventDefault();
}
Render() {
Return (
<form onSubmit={this.handleSubmit}>
<label>
Name :
<input type= “text” value={this.state.value} onChange={this.handleSubmit} />
</label>
<input type= “submit” value= “Submit” />
</form>
);
}

29. How much do you know about controlled and uncontrolled components?

Controlled component	Uncontrolled component
Not maintaining your status	Keep your own state
2. Data is controlled by the parent component	2. Data is controlled by DOM
3. Get the current value via props and then notify the change via a callback	3. Refs is used to get its current value

30. What is a high-level component (HOC)?

High-level components are an advanced method of reusing component logic and are a component pattern derived from React. A HOC is a custom component that contains another component within it. They can accept any dynamics provided by subcomponents, but will not modify or copy any of the behaviors in their input components. You can think of HOC as a “Pure” component.

31. What can you do with HOC?

HOC can be used for many tasks, such as:

Code reuse, logic and boot abstraction
Render hijacking
State abstraction and control
Props control

32. What is a pure component?

The Pure component is the simplest and fastest component that can be written. They can replace any component that only has render() . These components enhance the simplicity of the code and the performance of the application.

33. What is the importance of the key in React?

Key is used to identify the unique Virtual DOM element and its corresponding data for the driver UI. They help React optimize rendering by reclaiming all of the current elements in the DOM. These keys must be unique numbers or strings, and React simply reorders the elements instead of re-rendering them. This can improve the performance of your application.

React Redux

34. What are the main issues of the MVC framework?

Here are some of the main issues with the MVC framework:

Very expensive for DOM operations
The program runs slowly and is inefficient
Serious memory waste
Component models need to be built around models and views due to circular dependencies

35. Explain Flux

Flux is an architectural pattern that enforces one-way data flow. It controls derived data and uses a central store with all data permissions to communicate between multiple components. Data updates throughout the app must only be made here. Flux provides stability for applications and reduces runtime errors.

36. What is Redux?

Redux is one of the hottest front-end development libraries available today. It is a predictable state container for JavaScript programs for state management of the entire application. Applications developed with Redux are easy to test, can run in different environments, and display consistent behavior.

37. What are the three principles that Redux follows?

Single fact source: The state of the entire application is stored in the object/status tree in a single store. A single state tree makes it easier to track changes over time and debug or inspect applications.
The state is read-only: the only way to change the state is to trigger an action. Actions are ordinary JS objects that describe changes. Just as state is the smallest representation of data, this operation is the smallest representation of data changes.
Change with a pure function: In order to specify how the state tree is transformed by operation, you need a pure function. Pure functions are functions whose return values depend only on their parameter values.

38. What is your understanding of the “single source of truth”?

Redux uses “Store” to store the entire state of the program in the same place. So the state of all components is stored in the Store and they receive updates from the Store itself. A single state tree makes it easier to track changes over time and debug or check the program.

39. List the components of Redux.

Redux consists of the following components:

Action – This is an object that describes what happened.
Reducer – This is a place to determine how the state will change.
Store – The state/object tree of the entire program is saved in the Store.
View – displays only the data provided by the Store.

40. How does the data flow through Redux?

41. How do I define an Action in Redux?

The Action in React must have a type attribute that indicates the type of ACTION being executed. They must be defined as string constants and more properties can be added to them. In Redux, actions are created by functions called Action Creators. The following are examples of Action and Action Creator:

function addTodo (text) {
Return {
Type: ADD_TODO,
Text
}
}

42. Explain the role of the Reducer.

Reducers are pure functions that specify how the state of an application changes in response to an ACTION. The Reducers work by accepting the previous state and action, and then it returns a new state. It determines which update needs to be performed based on the type of operation and then returns the new value. If you do not need to complete the task, it will return to its original state.

43. What is the meaning of Store in Redux?

The Store is a JavaScript object that holds the state of the program and provides methods to access the state, dispatch actions, and register listeners. The entire state/object tree of the application is saved in a single store. Therefore, Redux is very simple and predictable. We can pass the middleware to the store to process the data and record the various operations that change the state of the storage. All operations return a new state via the reducer.

44. What is the difference between Redux and Flux?

Flux	Redux
1. Store contains state and change logic	1. Store and change logic are separate
2. There are multiple stores	2. There is only one store
3. All stores do not affect each other and are level	3. A single store with a layered reducer
4. There is a single scheduler	4. No concept of scheduler
5. React component subscription store	5. The container components are linked
6. The state is variable	6. The state is immutable

45. What are the advantages of Redux?

The advantages of Redux are as follows:

Predictability of results – Since there is always a real source, store, there is no question of how to synchronize the current state with the rest of the action and application.
Maintainability – Code becomes easier to maintain, with predictable results and a strict structure.
Server-side rendering – you just need to pass the store created on the server to the client. This is very useful for initial rendering and can optimize application performance to provide a better user experience.
Developer Tools – From operations to state changes, developers can track everything that happens in the app in real time.
Community and Ecosystem – There is a huge community behind Redux that makes it even more fascinating. A large community of talented people contributed to the improvement of the library and developed various applications.
Easy to test – Redux’s code is primarily small, pure and independent. This makes the code testable and independent.
Organization – Redux accurately illustrates how the code is organized, which makes the code more consistent and simple when used by the team.

React routing

46. What is React routing?

React routing is a powerful routing library built on top of React that helps add new screens and streams to your application. This keeps the URL in sync with the data displayed on the web page. It is responsible for maintaining standardized structures and behaviors and for developing single-page web applications. React routing has a simple API.

47. Why is the switch keyword used in React Router v4?

Although <div> a plurality of Routing Encapsulation Router, when you want to display only a single route to be rendered more defined route, you can use the “switch” keyword. When used, the <switch> tag matches the defined URL to the defined route in order. When the first match is found, it renders the specified path. Thereby bypassing other routes.

48. Why do I need a route in React?

The Router is used to define multiple routes. When a user defines a specific URL, if the URL matches the path of any “route” defined in the Router, the user will be redirected to that particular route. So basically we need to add a Router library to our application, allowing multiple routes to be created, each providing us with a unique view

<switch>
<route exact path=’/’ component={Home}/>
<route path=’/posts/:id’ component={Newpost}/>
<route path=’/posts’ component={Post}/>
</switch>

49. List the advantages of the React Router.

Several advantages are:

Just like React is based on components, in React Router v4, the API is ‘All About Components’ . You can visualize the Router as a single root component ( <BrowserRouter>) where we will be specific to the child route (<route> wrap ).
There is no need to manually set historical values: in React Router v4, all we have to do is wrap the route in <BrowserRouter> assembly.
The packages are separate: there are three packages for the Web, Native, and Core. This makes our application more compact. It is easy to switch based on a similar coding style.

50. What is the difference between React Router and regular routing?

theme	Conventional routing	React routing
Participated page	Each view corresponds to a new file	Only involves a single HTML page
URL change	The HTTP request is sent to the server and the corresponding HTML page is received	Change only history properties
Experience	The user actually switches between different pages of each view	The user thinks they are switching between different pages

I hope this React interview question and answer will help you prepare for the interview. wish all the best!

How the blockchain will affect open source

Tech

admin

-

March 24, 2019

0

How the blockchain will affect open source

Blockchain technology, like the Internet, profoundly affects the technology of human society, and blockchains are evolving and constantly trying to find their place. In any case, one thing is certain, that is, the blockchain is a disruptive technology that will fundamentally change some industries. I am convinced that open source is one of them.

At the beginning of the establishment of Bitcoin in the past ten years before Nakamoto, it attracted many followers and slowly evolved into a decentralized movement. Even for some people, blockchain technology is as profoundly affecting the technology of human society as the Internet. Of course, a large number of people believe that the blockchain is just another Ponzi scheme. In this debate, the blockchain is also evolving and constantly trying to find its place. In any case, one thing is certain, that is, the blockchain is a disruptive technology that will fundamentally change some industries. I am convinced that open source is one of them.

Open source model

Open source is a software collaborative development method and a software distribution model. Open source allows people with common interests to work together to produce things that no one in them can accomplish independently. It makes the value created by the whole much greater than the part. Sum. Open source distributes and protects through distributed collaboration tools (IRC, email, git, wiki, issue tracking, etc.), as well as open source license models, and of course non-profit funds such as the Apache Software Foundation and the Cloud Foundation Governance.

For a long time, the most curious thing about the open source model is the lack of financial incentives. In the open source world, like other aspects of human society, a lot of factions, such as some of them, think that talking about open source should not talk about money. Open source should be the inner freedom of incentives and resource behavior (such as “common ideals” “For the great things”); there are others who believe that open source needs to be externally, especially financially motivated. Although the open source project is only ideally romantic through the world’s volunteers, as far as the current status quo is concerned, in fact the main open source completion contribution is made in the case of payment. Of course, there is no doubt that we have a large number of unpaid contributors, but these contributions are temporary and recurring, or some of the sought-after projects have attracted worldwide attention. Establishing and maintaining open source projects requires companies to put a lot of effort and effort into developing, documenting, testing, and fixing defects, and it is continuous, as always, not a whim. Be aware that developing software products is something that needs to overcome a lot of difficulties. It is best to have money incentives to last.

Open source commercialization

As we all know, the Apache Software Foundation survives through donations, and of course there are other incomes: sponsorship, conference fees, and so on. But be aware that these funds are primarily used to run the foundation itself, such as providing legal protection for the project and ensuring that there are enough servers to run build programs, defect tracking, mailing lists, and more.

Similarly, the CNNF Foundation will charge membership fees and more conference fees, which are also used to run the foundation and provide resources for the project. In the years now, most of the software can’t be built on your own laptop. They are all running and testing in hundreds of servers in the cloud platform. These are the daily expenses of the Foundation. Others such as marketing activities, brand design, distribution of some small promotional items, is also a matter within the foundation. The core mission of the Foundation is to implement the right processes, interact with users, developers, and control mechanisms, and ensure that available financial resources are allocated to open source projects for mutual benefit.

It seems that everything is working fine, isn’t it? Open source projects can raise money and the foundation can be distributed fairly. So where is the problem?

What is not stated here is: value transfer between open source producers and open source consumers, direct, transparent, trusted, decentralized, automatic two-way links. For the moment, all links are one-way or indirect:

One-way : A developer (a developer in a broad sense, can be any role in software production: code farmers, maintainers, distributors), using their ingenuity, racking their brains, and spending countless hours developing open source Projects, and submit contributions to share this value for all open source users. But basically it is wishful thinking.
Indirect : If there is a bug in the software that affects a particular user/company, the following situations occur:
- It’s ideal to let internal developers fix bugs and then submit a pull request (PR). These companies are not always able to hire developers for specific open source projects because the average company will use hundreds of thousands. An open source project.
- Hire freelancers who specialize in this particular open source project and pay for the service. Ideally, freelancers are also submitters of open source projects, and can quickly change project code directly. Otherwise, the fix may never enter the upstream project.
- Close to companies that provide services around open source projects. These companies typically employ open source committers to influence and gain community credibility and provide products, expertise and professional services.

The third option is to maintain a successful model for many open source projects. Whether these companies provide services (training, consulting, workshops), technical support, packaging, open core, or SaaS services, it’s undeniable that they all need to hire hundreds of full-time employees to work on open source, we can see There are a lot of such companies, they have successfully established an effective open source business model, and more companies are joining the camp.

Companies that support open source projects play an important role in this ecosystem: they are an important catalyst between open source projects and users. Companies that can truly create value for their users are not just able to package great software; they are able to identify the real needs of users and gain insight into technology trends, the ability to create a complete stack or even an open source project. Ecosystems to meet these needs. They can devote themselves to a somewhat lonely and boring project, and will always support it for many years, just to stick to its value. And if a section is missing from a software stack, they can start an open source project from scratch and build a community around it. They can even buy a closed source company and then open up the project entirely (yes, maybe many readers have already guessed which company it is talking about here, yes, the features here are owned by Red Hat. .)

To sum up, the open source model based on commercialization is like this. The project is managed and controlled by a small number of individuals or companies. The individuals or companies ensure the successful release of the project, and they are commoditized and effective. In giving back to the open source ecosystem. For open source developers, management companies and end users, this is a beautiful pattern without losers. This can be a good alternative to those expensive and closed source software!

Self-supply, decentralized open source

There is no doubt that if you want to make a good reputation for your project, you have to meet some people’s expectations. For example, both the Apache Software Foundation and the Cloud Native Computing Foundation require a process of incubation and graduation. In addition to all technical and formal requirements, the project must have a healthy number of active committers and users. These are the keys to a sustainable open source project. Having source code on GitHub is fundamentally different from having an active open source project. An active open source project means the author of the code and the user who uses the code. The two groups grow spirally by exchanging value and forming an ecosystem that everyone benefits. Some project ecosystems may be small and have a short life span, and some may include multiple projects and competing service providers, with very complex interactions that last for many years. But as long as there is a value exchange, everyone benefits, and the project is developed, maintained and sustainable.

Let’s take a look at Attic, the Apache Software Foundation project, which has completed its historic mission and is moving into the final stages of its lifecycle. This is a very normal phenomenon: when a project is technically no longer suitable for its original development purpose, it usually ends naturally. Similarly, at the ASF incubation base, you will find that many projects have never graduated but have already withdrawn from the historical arena. Usually, these projects cannot build a large enough community, either because they are too biased or better. The program is replaced.

But more often than not, projects with high potential and superior technology cannot sustain themselves because they cannot form or maintain an effective ecosystem for value exchange. The current open source model and foundations do not provide developers with a framework or mechanism to get paid or let users know their requests, so that no one has a common value commitment. In this case, the result is that some projects can only maintain themselves in a commercial open source environment. In commercial open source, the company acts as a middleman and gains value between developers and users. This also adds another limitation and requires the service provider’s company to maintain some open source projects. This seems to be far from our ideal situation: users can fully and directly express their expectations of the project, developers can deliver their commitment to the project in a transparent and quantifiable way, which is a common interest and A community that intends to exchange value.

Now you can imagine that there is such a model, its working mechanism and tools can directly deal with open source users and developers. This is not only reflected in contributing code through pull requests, sending messages using mailing lists, the number of stars on GitHub, and stickers on laptops, but also in ways that users have more ways, more self-control, and transparent behavior. To influence the direction of the project.

The model can include incentives for the following behaviors:

Funding directly for open source projects, not through software foundations
Influence the direction of the project by voting (via token holders)
Functional requirements driven by user needs
Timely merge pull request
Give rewards to those who submit defects
Reward for better test coverage
Reward to update the document in time
Timely security fix
Expert assistance, support and service
Best budget for the project’s preachers and promoters
Regular activity budget
Faster email and online chat help system
Fully understand the status of the overall project, etc.

Smart clerks may have guessed it, yes, the above talks about using blockchains and smart contracts to achieve positive interaction between end users and developers. Smart contracts allow token holders to have real power to influence the direction of the project.

The figure above shows the application of blockchain in the open source ecosystem.

In the current open source ecosystem, it is possible to use abnormal means to influence the direction of the project, such as the financial commitment of the service provider and the limited way of passing the foundation. But adding blockchain-based technology to the open source ecosystem opens up a new channel between users and developers. This is not to say that it will replace the commercial open source model; because most open source companies do a lot of intelligence. What the contract can’t do. But smart contracts can trigger a new type of open source project that provides a second-life opportunity for those overwhelmed projects. It motivates developers to claim boring pull requests, write documentation, test program code, and more, providing a direct source of value exchange between users and open source developers. Even if company support is not feasible, the blockchain can add new channels to help open source projects grow and achieve self-sustainment in the long run. It can create a new complementary model for self-sustaining open source projects – a win-win model.

Pass open source

In fact, there are already many implementations aimed at open source certification. Some of them are only focused on the open source model, and some are more general (also applicable to the open source model). The following is a list I collected:

GitCoin , which grew up in open source, is one of the most promising open source projects in the field.
Oscoin , a cryptocurrency for open source.
Open collaboration , a platform that supports open source projects.
FundYourselfNow , for project crowdfunding and ICO platforms.
Kauri , supporting open source project documentation.
Liberapay , a regular donation platform.
FundRequest , a decentralized market for open source collaboration.
CanYa , recently acquired by Bountysource , is the world’s largest open source P2P bounty platform.
OpenGift , a new model for open source cashout .
Hacken , a white hat token for the Hackers .
CoinLancer , a decentralized human market.
CodeFund , an open source advertising platform.
IssueHunt , a fundraising platform for open source maintainers and contributors.
District0x 1Hive , crowdsourcing and curation platform.
District0x Fixit , GitHub Defect Reward System.

This list is still growing at the time of this writing, and it’s pretty fast, some of them will definitely disappear, and some will shift the target, but there will always be some integrations such as SourceForge , Apache Software Foundation, and GitHub. . These platforms don’t and do not need to replace these platforms, but the token model is a good complement to these platforms, which can make the open source ecosystem richer. Each project can choose its distribution model (license), management model (foundation), and incentive model (token). Either way, it will be an open source world like fresh blood!

Open and decentralized future

Software is consuming the world
Every company is a software company
Open source is an innovative field

The fact is that the open source has developed into such a huge industry, it will not easily fail, and open source is too important for the world. It is impossible for a few to be manipulated or abandoned by the world to fend for itself. Open source is a shared resource system that is valuable to everyone, and more importantly, it can only be managed in such a way that all companies in the world want to have their own chips and voice in open source, however Unfortunately, we don’t have a tool or a habit to do this. Our expectation for the tool is that these tools will allow anyone to express their appreciation or neglect of the software project; it will be in producers and consumers. A direct and faster feedback loop between developers and users; it promotes a dual innovation model driven by user needs and is tracked and measured by tokens.

How to easily upload videos to YouTube

Tech

admin

-

March 23, 2019

0

YouTube, the world’s most popular video sharing service

YouTube is the world’s largest video services company, reportedly uploading 24 hours of video per minute.Although I have seen the video, it is quite a threshold and uploads the video very much, let alone not a lot, even those who are Irassharu think that we need special software or use the text on the screen with BGM?In fact, not only can you upload movies, edits such as turning on BGM, placing comments in movies, and using tools on YouTube. Easy to edit without special software.You can also set the scope of the disclosure, for example, to allow only friends, acquaintances, and video families to watch videos and movies, and to grow children when traveling with friends.This time I will explain how to easily publish and edit on the YouTube website.

File format, time, capacity that can be uploaded to YouTube

The file formats that can be uploaded to YouTube are as follows (some PCs, devices, tools, etc. cannot be upgraded properly).

Windows Media Video (.WMV).3 GP (Mobile).WMV (Windows).MOV (Mac).MP4 (iPod / PSP).MPEG.FLV (Adobe Flash ).MKV (h.264)in addition to the above format In the case of an external save format, it must be converted to one of the save formats by using video conversion software or the like. YouTube recommends using video in MPEG4 format.The capacity of one upload is 2 GB and the length is within 10 minutes. If it is another movie, split the movie file once and upload it after keeping the capacity and length within the specified range.

Upload a video from the YouTube website using a browser

To upload your video to YouTube, you’ll need to sign in after signing up for YouTube. If you have not yet registered as a member, click on “Create Account” in the top right corner of the YouTube screen and register as a member.1. Click UploadOnce you’re signed in to YouTube, click the “Upload” link at the top of the page on the right side of the search window. Click to display the upload page.

The upload link is at the top of the home page, next to the search window.

2. ChooseClick “Upload Video” for the video you want to upload, then select the video you want to upload. The upload will begin and the detailed settings screen will be displayed.

The capacity that can be uploaded at one time is 2 GB and the length is less than 10 minutes.

When uploading, if you set up the “automatic notifications” feature, you can post information about your uploaded videos and videos that have been registered as favorites to your friends, Twitter fans, and more. To use this feature, simply click on the “Connect account” link to connect to your YouTube account.3. Enter the title, description, label and category of the video.

We recommend that you fill in the title, description, tags, etc. during the upload phase.

Fill in the title and description, then select the category that is appropriate for uploading videos from the drop-down menu.The tag automatically displays the candidate tags based on the video content on the YouTube side. Although it is good to use it, in the case of only Japanese animation, it is best to write it yourself because the accuracy is not so good.4. Set up the movieThe scope of the disclosure is to set the scope of the disclosure,

Anyone can search and play “Public”,
“Private Post” can only be viewed by users who don’t see search results,
browse pages or channels but know the URL to view
only “private”
for specified users (having an account on YouTube)

There are three types to view.

Even if it’s set to private, you can share it with up to 25 users.

“Public” if you want to see more users (such as events and your live video), or “Private” if you only want specific users to see the child’s growth and private videos.Basically, you can’t see “Private Limited” except for users who know the URL, but in some cases, URLs that you don’t know at all will know that the danger is not zero. If you don’t want to show it to friends and family, we recommend that you always make it “Private.”Even if you make it “private”, you can’t upload movies, plays, ads, music videos, etc. without permission.When the upload of the video is completed, the URL of the video and the HTML tag used to paste the video on a website other than YouTube, such as a blog, will be displayed.

The URL shown here will be the URL of the video you uploaded.

Even after the movie is released, the above information, the disclosure range setting can be changed any number of times.

Upload videos recorded with webcam, etc. now

As of July 2010, YouTube cannot be streamed like USTREAM, but you can immediately upload content recorded using your webcam. By using it, you can easily upload the recorded one immediately, without having to spend time and effort as much as the previous page, regardless of the movie format.1. On the Upload Movie File screen, click Record from webcam.

With a webcam, you can batch record, save and upload on YouTube.

2. A pop-up screen will appear asking if you are allowed to access the camera and microphone, so click Allow.

Be sure to connect using the connected webcam.

3. Since the “Ready to Record” button appears, click it. The recording will begin.You can easily record when you check the recorded images on the screen.

When recording, the black circle button on the lower left will light red, so if you want to end the recording, click the circle that lights up in red.4. Set video information, etc.When the recording is complete, three buttons will be displayed. If you want to publish now, click Publish. When displaying the title and description and the open range settings screen, fill them in, set them up and save them.

Publish, re-record, preview you just click the All 1 button.

If you want to view the recorded content, click Preview. If you want to redo the recording again, click Re-Record.When you click Publish, the movie will play. If you want to make your disclosure private or private, please set your disclosure now. The title, description, etc. can be completed later.

Upload a movie from your phone

In addition to smartphones such as iPhones and Android phones, you can now shoot high quality movies on most mobile phones. You can also easily upload this video to YouTube.To upload a video taken with your phone, click “Settings” in “Upload directly from your phone to YouTube” on the right side of the “Upload Video File” page.Click “Settings” to create your own upload email address

Create a target email address for the movie. Just send a movie with a movie with this email address.When sending an email, place the subject name to make it the title of the movie, and the name written in the email text becomes the explanatory text. You can create and change on the site later, but if you want to publish quickly, enter the title and description text when you send the message.

5 free tools to make data science easier

Tech

admin

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February 27, 2019

0

5 free tools to make data science easier

One of the great advantages of data science is that many of the most advanced tools used by data scientists are free. In fact, the number of free tools in the industry is already very large, and sometimes it can be a headache, I don’t know how to choose. To help you determine which tools you should choose, here are five free software tools worth knowing about data processing.

Anaconda Distribution

Python has become a great tool in the field of data science because a large number of developers have built Python-based data science libraries. For data scientists working in Python, libraries such as NumPy, SciPy, panda, and scikit-learn are essential. Unfortunately, even for the most experienced developers, dealing with all of these Python libraries is a challenge. They can be difficult to install, and many rely on some software other than Python.

Anaconda is a free Python distribution and package manager that solves this problem. The Anaconda Python distribution comes pre-installed with more than 200 of the most popular data science Python libraries, and its package manager provides an easy way to install over 2,000 additional packages without worrying about software dependencies. Anaconda comes with many other popular tools, including Jupyter Notebook, which enables data scientists to work interactively in a browser-based environment.

RStudio & RStudio Server

RStudio is an integrated development environment (IDE) tailored for performing interactive data analysis and more formal programming in the R language. RStudio provides a perfect balance for an interactive work environment that supports R consoles and data visualization panels, as well as a full-featured text editor for syntax highlighting and code completion.

One less well-known tool is RStudio Server, a full-featured version of the RStudio IDE that runs on the server and is accessible through a browser. This means you can access RStudio IDE from anywhere via a network connection and transfer computing to dedicated resources. This allows data scientists to process potentially sensitive data without having to download it to a personal device, or perform complex and computationally intensive work with R on any device.

OpenRefine

Originally developed by Google engineers, OpenRefine is an open source tool for data cleansing. It allows practitioners to read confusing or corrupted data, perform batch conversions to fix errors, generate clean data, and export the results in a range of useful formats.

One of the best features of OpenRefine is that it tracks every action performed on a dataset, making step tracking and workflow re-creation very easy. This is especially useful when you have many files with the same data integrity issues and you need the same conversion. OpenRefine allows you to export a sequence of changes made to the first data file and apply it to a second data file, saving you the time of rework and reducing the possibility of human error.

OpenRefine also provides a very powerful tool for handling messy text fields. For example, if there is a column in the data set, the entry is “Vancouver, BC.” , “VANCOUVER BC” and “vancouver bc”, OpenRefine’s text clustering tool will recognize that they may be the same and perform a batch conversion to apply a single label to each event.

Apache Airflow

In most organizations, data is not stored in one place, nor is it accessed using only one method. There are often multiple databases, data storage systems, APIs, and other processes to track data across the organization. The data team’s main job is to move the data from where it resides to where it needs to be analyzed and convert as needed. Ideally, this work should be as automated as possible, and Apache Airflow can do that.

Airflow was developed by Airbnb engineers for internal use and was open sourced in 2015. It is a tool for mapping, automating, and scheduling complex workflows that involve many different systems with interdependencies. It monitors the success of these processes and alerts engineers when problems arise. Airflow also has a web-based user interface that represents the workflow as a small job network so that dependencies can be easily visualized.

H2O

With the maturity of machine learning technology, some basic algorithms have been widely used. Generalized linear models, tree-based models, and neural networks have become essential elements in machine learning toolkits. However, although many implementations of algorithms in R and Python are useful for prototyping and proof of concept, they do not scale well into production environments.

H2O is an open source tool that provides an efficient and scalable implementation of the most popular statistical and machine learning algorithms. It can connect to many different types of data storage systems and can run on any device, from laptops to large computing clusters. It has powerful and flexible tools for building model prototypes and fine-tuning, and the models built in H2O are very easy to deploy into production environments. Most importantly, H2O has Python and R APIs, so data scientists can seamlessly integrate it with existing environments.

There are so many software tools in the field of data science. When the project starts, it is a good choice to choose a good enough free tool to speed up and optimize the data flow.

Some basics in Python data analysis

Tech

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February 27, 2019

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Mathematics and statistics

Mathematical analysis involves a large amount of mathematical knowledge, and the mathematical knowledge involved in the data processing and analysis process can be quite complex. Therefore, it is very important to have a solid mathematical foundation. At least it is necessary to understand what is being done. It is also necessary to be familiar with the commonly used statistical concepts, because all the analysis and interpretation of the data are based on these concepts. If computer science provides data analysis tools, then statistics provide the basic concepts.

Statistics provides a lot of tools and methods for analysts, and it takes years of honing to master them all. The most commonly used statistical techniques in the field of data analysis are: 1. Bayesian method; 2. Regression; 3. Clustering; when these methods are used, it will be found that mathematical and statistical knowledge are closely combined, and both Very high demand.

Machine learning and artificial intelligence

One of the most advanced tools in the field of data analysis is the machine learning method. In fact, although data visualization and techniques such as clustering and regression are very helpful for analysts to find valuable information, in the data analysis process, analysts often need to query various patterns in the data set. These steps are very professional. Strong.

The discipline of machine learning is how to combine a series of steps and algorithms, analyze data, identify patterns in the data, find different clusters, find trends, and extract useful information from the data for data analysis. And automate the entire process.

Machine learning is becoming a fundamental tool for data analysis, so understanding its importance to data analysis is not a problem.

Data source field

Knowledge in the field of data sources is also a very important piece. In fact, although the analyst has been trained in statistics, he must also go deep into the application field and record the raw data to better understand the process of data generation. In addition, the data is not just a dry string or number, but an expression of the actual observed parameter, or more specifically its metric. Therefore, an in-depth understanding of the data source area can enhance the ability to interpret data. Of course, even for analysts who are willing to learn, it takes a lot of work to learn the knowledge of a particular field. Therefore, it is best to ask relevant experts in a timely manner.

Understand the nature of the data

The object of data analysis is naturally data. Data is a primary concern at all stages of data analysis. The raw materials to be analyzed and processed are composed of data. After processing and analyzing the data, you may end up with useful information. This information can increase the understanding of the research object, that is, the system that produces the raw data.

Data to information transformation

Data is a record of everything in the world. Anything that can be measured or classified can be represented by data. Once the data has been collected, it can be studied and analyzed to understand the nature of the thing. People often use them to make predictions, or even if they don’t make predictions, they can at least make the speculation more relevant.

When information is transformed into a set of rules that help to better understand a particular mechanism, it is said that information has been transformed into knowledge, and we can use this knowledge to predict the evolution of events.

The data can be divided into two different types: 1. The categorical type has a classification and sequencing; 2. The numerical type has discrete and continuous data; the categorical data refers to values or observations that can be divided into different groups or categories. There are two types of data: class and order. There is no intrinsic order for the categories of the fixed type variables. There is no intrinsic order for the categories of the ordered variables, and the ordered variables have a pre-specified order.

Numerical data refers to values or observations obtained by measurement. There are two different types of numerical data: discrete and continuous. The number of discrete values is countable, and each value is distinguished from other values. Conversely, continuous values result from measurements or observations whose results fall within a certain range.

Data analysis process

The data analysis process can be described in the following steps: transforming and processing raw data, presenting the data visually, and modeling for prediction. Therefore, data analysis is nothing more than the following steps, each of which plays a role in the next few steps. Therefore, data analysis can be roughly summarized as a process chain consisting of the following stages:

Problem definition, data extraction, data cleansing, data transformation, data exploration, predictive models, model evaluation/testing, results visualization and interpretation, solution deployment.

Do you understand the http protocol?

Tech

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February 27, 2019

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HTTP protocol

In order to better understand the HTTP protocol, let’s take a brief look at the TCP/IP protocol family. Usually the network we use is based on the TCP/IP protocol family, and HTTP is no exception.TCP/IP protocol family

The client and the server communicate with each other, and both parties must follow the same rules, such as:1 How to detect the communication target2 Which side initiates the communication first3 Which language is used for communication4 How to end the communication5 Different hardware and operating system How to communicate

All this requires a certain constraint rules, we say the rule is the protocol .Layered management of TCP/IP

One of the most important features of the TCP/IP suite of protocols is layering. The TCP/IP protocol family is divided into the following four layers: the application layer, the transport layer, the network layer, and the data link layer (the OSI reference model is divided into seven layers).Application layer

Role: The application layer determines the activities of communication when providing application services to users. Eg. DNS, FTP, HTTP.2. Transport layer

Role: The transport layer provides the data transfer between the two computers in the network connection to the upper application layer. Eg. UDP, TCP.3. Network layer

Role: The network layer is used to process packets flowing over the network. A packet is the smallest unit of data transmitted by the network. This layer specifies the path to the other party’s computer and passes the packet to the other party.4. Link layer

Role: Used to handle the hardware part of the connected network. This includes physical controls such as control of the operating system, hardware device drivers, NICs, and fiber optics.Protocols that are closely related to HTTP: IP, TCP, and DNS

1. IP protocol responsible for transmission

According to the hierarchy, the IP is located at the network layer;the role of the IP protocol is to transmit various data packets to each other, and to ensure delivery to the other party, various conditions must be met, two important conditions being the IP address and MAC address. ;communication between the MAC address-dependent IP, ARP protocol employed to communicate with the MAC address.MAC (Media Access Control) address, also called hardware address.

To put it bluntly, the MAC address is like the ID number on our ID card and is globally unique. We can assign an arbitrary IP address to a host as needed. Once any network device (such as a network card or router) is produced, its MAC address cannot be modified by the configuration in the local connection. If the network card of a computer is broken, the MAC address of the computer changes after the network card is replaced.

2. Ensure reliable TCP protocol

According to the hierarchical, TCP is located at the transport layer, providing a reliable byte stream service. Theso-called byte stream service means that, in order to facilitate transmission, the large block data is divided into packets in units of segments for management.

A reliable transmission service means that data can be accurately and reliably transmitted to the other party.In a nutshell, the TCP protocol splits the data in order to make it easier to transfer big data, and the TCP protocol can confirm whether the data is sent to the other party.

3. DNS service responsible for domain name resolution

DNS is located at the application layer like the HTTP protocol, providing resolution services between domain names and IP addresses.

4. Relationship between various protocols and HTTP protocol

When sending a request, if the requested address is a domain name, the HTTP server first accesses the DNS server to obtain the IP address of the target server, and then generates an HTTP request message, which is sent to the TCP layer and transmitted to the target server according to the TCP/IP communication transport stream. .What is HTTP?

The HyperText Transfer Protocol (HTTP) is the most widely used network protocol on the Internet. It is the cornerstone of WWW (World Wide Web) to achieve data communication.It is an application layer protocol (the top level of the OSI seven-layer model) that delivers data (HTML files, image files, query results, etc.) based on the TCP/IP communication protocol.

The HTTP protocol is used for communication between the client and the server, and communication is achieved through the interaction of the request and the response (it is sure to establish communication from the client first, and the server will not send a response until it receives any request).

HTTP is a protocol that does not save state. In order to implement the desired state of saving state, cookie technology is introduced.

Protocol function

The HTTP protocol (HyperText Transfer Protocol) is a transport protocol for transmitting hypertext from a WWW server to a local browser. It can make the browser more efficient and reduce network transmission.

It not only ensures that the computer transmits the hypertext document correctly and quickly, but also determines which part of the document is transferred and which part of the content is displayed first (such as text before the graphic).The website address we enter in the address bar of the browser is called the URL (Uniform Resource Locator).

Just like every household has a house address, each page also has an Internet address. When you enter a URL in the browser’s address box or click on a hyperlink, the URL determines the address to browse. The browser extracts the webpage code of the site on the web server through the Hypertext Transfer Protocol (HTTP) and translates it into a beautiful webpage.working principle

An HTTP operation is called a transaction, and its working process can be divided into four steps:First the client and server need to establish a connection. Just click on a hyperlink and the work on HTTP begins.After the connection is established, the client sends a request to the server in the format of a Uniform Resource Identifier (URL), protocol version number, followed by MIME information including request modifiers, client information, and possible content.

After receiving the request, the server gives corresponding response information in the format of a status line, including the protocol version number of the information, a successful or erroneous code, followed by the MIME information including server information, entity information, and possible content.The information returned by the client receiving server is displayed on the user’s display through the browser, and then the client is disconnected from the server.

If an error occurs at a certain step in the above process, the error message will be returned to the client and output by the display. For the user, these processes are done by HTTP itself. The user just clicks with the mouse and waits for the information to be displayed.HTTP message

The information used for the HTTP protocol interaction is called an HTTP packet. The packet requested by the client is called a request packet. The packet that the server responds to is called a response packet.

HTTP packets can be roughly divided into two parts: the packet header and the packet body. Both are divided by the initial blank line (CR+LF). Usually, there is no need to have a message body.

Things to keep in mind while doing guest posting

Blogging

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February 21, 2019

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Things to keep in mind while doing guest posting

Let’s begin the discussion by understanding the terms ‘guest ‘. It means to post one’s content on others’ blog. Guest blogging is a great resource for exposure, outreaching, expanded branding, establishing expertise and to build credibility. If one is capable of following the given strategies, it’s a duck soup to get his content posted.

The crucial step to guest posting is the choice of website for sharing our work.

Research

One must go through excessive research on various websites and jot down the potential ones. The website must be capable of engaging long term readers. In this way, it is highly likely that our content is reached out to as many audience as possible. It is always advisable to go through the guest blogging guidelines of the respective website, as they provide a practical and ethical framework.

Few of the important topics one must focus on in these guidelines are for word count, accepted\appropriate topics the website allows, the lifetime of the post. After all, it’s the platform we choose that becomes our pathway to success

Pitching the idea

The first and foremost thing a person has to look after is to reach out to the admin of the blog and pitching them your idea. Pick an eye-catchy subject that will leave him almost undeniable to reject your mail. We must be really persuasive while debating about how beneficial it is for both the parties. Focus on why you believe that your work has to be published on their website. A good email with appropriate use of terms will do the work.

Be Unique

When it comes to guest posting, our content has to be stand-out among the rest. For this, the choice of topic plays a key role. One must not choose from an outdated topic which might not be in the best interest of the reader.

A high quality, well-written, statistically driven and perfectly versed content is the one that grabs attention. Our work has to be able to reach the reader’s expectations.

Thorough research on the topic has to be done and practical facts are to be taken into consideration to back up our claims. We should always stay relevant to the website’s content. You can link the previous work of your own site or previous blogs to the current one which is likely to show your expertise on blogging.

Being fully aware of the blog’s content is the key role in pitching our post. Deviating from it might often land you in trouble, so one must always stay in the track about his content.

Read the various articles posted on their site so as to get a gist of the topics chosen. Pour in all your thoughts and explore your knowledge on a particular topic.

Be open to receiving insightful feedbacks from fellow contributors and audience. This will widen your ideas and help you in creating more efficient content. Engaging with the audience is often seen as a good trait when it comes to blogging. Make sure to promote your work among your own audience through social media and various platforms.

You might also like to know about what backlink means an how to get it easily.

Conclusion

With the help of above guidelines one can ensure their guaranteed success and fame among co-bloggers. Hoping this article has provided required insights, thank you..

What does backlinks mean & practical ways to get easily

Tech

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January 30, 2019

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What does backlinks mean & practical ways to get easily

Recently, many seo novice friends have mentioned the concept of website backlinks, and the role of backlinks is quite intense. It is a good thing to argue that everyone is thinking hard and have their own opinions. So what exactly is the backlink? In this article, the author elaborates on the meaning, function, method, and query of backlinks.

What does backlink mean?

As the name implies, a backlink is a reverse link. For example, if document B has a link to document A, then the link is a backlink for document A.

There is a disagreement here, that is , the relationship between backlinks and outer links . Traditionally, backlinks refer to links to other pages outside the page; outer links refer to links to other sites outside the site (domain name).

The keyword ranking is based only on the page (of course, the page inherits the main domain name to a certain extent, which is the overall weight of the website). The author believes that the back link and the outer chain can be discussed as a meaning, because in terms of the target page, other The link to the page can be considered as an external link regardless of whether the domain name is the same or not.

In addition, it should also be noted here that friendship links are also considered in the context of backlinks. If you are looking for a wordpress seo monitoring plugin then check here seotoptool.com

Second, the role of backlinks

For the role of backlinks, the author believes that there is no need to explain too much, because the answer is very clear, for example, is conducive to page inclusion , keyword ranking and so on.

Third, the way of backlinks

Formally, backlinks can be divided into URL links and anchor text links. The difference is that the text in the A tag is different. The former uses the URL and the latter uses the keyword text.

Different forms have different roles. If you want to promote the URL, you can directly link to the URL. If you want to improve the ranking of the target keyword, it is recommended to use the anchor text link.

Fourth, how to do backlinks

In fact, for the role of backlinks, everyone basically agrees, the key issue is how to do backlinks. Some people think that traditional practices still fail, and some believe that traditional practices are still useful.

The author believes that traditional practices such as blogs, forums, etc. have a role to do with links, but their main role is to attract spiders to crawl URLs rather than keyword rankings. As for the backlinks that are good for improving keyword rankings, the author thinks that there are several links such as friendship links, single links, news source links, and other websites’ self-forwarding links.

Friendship link. Take the initiative to find industry, data-related websites, request exchange links, and more.
Single chain. There are two main ways for a single chain. One is to find a friend to help with the single chain, and the other is to buy a link. Need to pay attention to the purchase link is risky, must pay attention to the quantity and quality, the number of purchases can not be increased, and there is a link to buy a regular website.
News source link. Paid to publish a press release with a link in the content of the press release.
Other links. For example, by writing a soft article, the article has a link, and other webmasters agree with the article’s point of view and forward it. Such a link is also a very good link.

Five, how to query backlinks

Under normal circumstances, use the domain command on the line, but this command is found to be a pure URL or a URL link, can not find the anchor text link. You can use some other tools to query.

Few practical ways of getting backlinks

Backlinks means that external websites have your website pointing to your website.
Method 1. Submit the website to the DMOZ directory, yahoo directory, ODP directory, some professional directory websites;

Method 2, contact industry associations or commercial organizations. The link weights of these non-profit websites are generally high, so the link exchange with these websites is also a very good means;

method 3, release press release, reasonable hyperlink in the press release, when this news After being reprinted by many websites, you can help you add a lot of backlinks to your website ;

Method 4, add your hyperlink to the forum signature. Frequently mix forums, post posts, resources should be used well;
method 5, create blogs, enrich blog content, reasonably add hyperlinks to your website in the blog;
method 6, search engine search “submit website, add Related keywords such as url” . In the searched webpage, you can add backlinks to your website ;

Method 7, add self-help link application function to yourself, and attract other websites to actively link with you;

Method 8, leave comments on other people’s blogs, try to be as daily as possible Do this, but don’t leave a spam comment. Even some blogs leave comments to get backlinks;

Method 9, to see what content is the fastest. Check out the Baidu Chinese Search Billboard and find recent search hot keywords. If your article appears on the top page of popular keyword search results, there will be a lot of traffic.

Method 10, buy backlinks, many webmasters have a very large number of resources, you can buy backlinks to them.

Backlinks can increase traffic to your site and give you an inquiry to increase your volume.

Best Apps for Sports Lovers

Games

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January 30, 2019

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Sports Apps are now trending all over the world where people are more interested in keeping money on events and sport teams. Betting will improve a human’s confidence levels or teaches them a lesson which cannot be forgotten. Have you ever heard about Sports Apps like Betway Sports and William Hill which are the Best Betting Sites available online for free. This article “Top 5 Best Sports Apps and Sites 2019” will provide you the Best Sports Apps and Sites with official links and download links.

There are so many Betting Apps and Sports Sites available on market which makes you confused and may fall in some faulty websites. So check out these Top 5 Best Sports Apps and Sites that are purely working and having a daily updates and progress with regular people.

How Sports Apps and Sites work

In order to use any of the Sports Apps and Sites, first the user has to create his account online and join the site. There are few Sports Apps and Sites which provide the user to register on their site for free. We have found that Beltway is one of the Best Betting Site in 2019 which is most suitable and highly recommended for Cricket Betting.

This site will allow users to transfer money from and to their wallet by using the Country Currency Rate. For example, if the user is keeping the Betting from India then the money will be added to the wallet in INR.

List of Top 5 Best Sports Apps

1. Betway Sports

Betway is the Best Betting App in 2019 which also has an Online Official Website. It is the most trusted site to start cricket betting and refer friends where you money transfers will be safe. This app is used by many people and has so many features which will definitely amaze the user and makes him the Best Gambler. Not only cricket betting, it also has Betting option for other Sports like NFL, NHL, NBA, MMA, Golf, Soccer, Horse Racing, and Tennis.

2. William Hill

William Hill Betting App is one of the Best Betting App that has the ability to claim the betting amount in most of the currencies. It will work on both iOS Devices and also on Android Devices. Betting is done on our fingertips by creating an account in it and finding a particular market where user can get various sports.

3. Bodog Sports

Bodog Sports is another Betting App which is similar to Betway App. The user can create account for free and he will get a reward amount for registering on their app. This amount will be alloted only for the new subscribers only. It works perfectly on iPhone, Android, Tablets, and BlackBerry phones.

4. Sports Interaction

Sports Interaction is a famous Betting App which is highly recommended by other country users. Even this app also gives the user a great welcome bonus that can be utilized for initial betting on sports. Later on the user can add money to the wallet and continue wagering on sports.

5. Pinnacle App

Pinnacle Betting App is mainly established for Big Sports and Leagues. It will show the each and every sports details and leagues that are available online with particular dates. Live sports also included in this along with the Casino Game which is a Best part on this app.

PrimeWire: Top List for Fast PrimeWire Mirror Sites [2019]

BEST GUIDE

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January 22, 2019

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PrimeWire: Top List for Fast PrimeWire Mirror Sites [2019]

Here, this guide for Top List for Fast PrimeWire Mirror Sites in this upcoming year and single brand PrimeWire and later in PrimeWire to watch latest movies online for free and also see updating the website very frequently to serve latest movies to its users as soon as possible. You’ll be able to find latest & old movies in lots of genres sort them by years, actors, and studio or search them directly through PrimeWire search box to watch your desired movie.

Here, this easy PrimeWire free movie streaming website made it very easy for people around the world to navigate to their desired movie and watch them fast PrimeWire servers and after you can access PrimeWire through its main domain primewire.ch that is best for all time.

PrimeWire

PrimeWire website might be blocked on your internet because your government banned it or ISP restricted access to the domain due to its illegal nature to serve free movie streaming and you can access by using any third party proxy website but using this speed loss and also face slow browsing that is so very bad in this case of movie streaming.

Primewire mirrors are used to stream the content, there is a competitor of primewire in the name of putlocker, and it also provides the same streaming option as primewire. You need mirrors because the main websites are closed or down in your location. Putlocker9 and Putlockerfilms.com is the same thing that we are talking in the article. It is also a mirror, and you can use it, in any case, these choices will not work for you in the future.

Here, you want to Access PrimeWire the best way to do is using PrimeWire Mirror Sites. PrimeWire Mirror sites are clones to the original PrimeWire website but they are available in different domains and also available for these PrimeWire, LetMeWatchThis and 1Channel proxies see below list for all alternatives for PrimeWire.

Top List for Fast PrimeWire Mirror Sites or primewire proxy

PrimeWire

primewire.unblocked.cab

primewire.immunicity.cab

primewire.bypassed.cab

primewire.unblocked.team

primewire.unblocked.pub

primewire.ltd

1channel.biz

primewire.ch

1Channel Proxy

PrimeWire UK Mirror

PrimeWire Proxy Sites are maintained either by official PrimeWire staff or internet provide unblock access to PrimeWire to all the people worldwide and site is blocked in their internet connection and also updating their PrimeWire Proxies to provide the latest content and also you want to browse proxies of other movie streaming and torrent websites then follow any of the see lots of mirrors of popular movies and TV shows streaming in this site.

Here, a complete guide for PrimeWire: Top List for Fast PrimeWire Mirror Sites [2018] and you read this guide very helpful for you.