How can i write this class component to react functional component.?

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functionalclassreactcomponent
90%

Passing Functions to Components,This function is a valid React component because it accepts a single “props” (which stands for properties) object argument with data and returns a React element. We call such components “function components” because they are literally JavaScript functions.,Uncontrolled Components

function Welcome(props) {
  return <h1>Hello, {props.name}</h1>;
}
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First of all, the clear difference is the syntax. Just like in their names, a functional component is just a plain JavaScript function that returns JSX. A class component is a JavaScript class that extends React.Component which has a render method. A bit confusing? Let’s take a look into a simple example.,See state with functional component in CodePen,Inside a functional component, we are passing props as an argument of the function. Note that we are using destructuring here. Alternatively, we can write it without as well.

import React from "react";
 
const FunctionalComponent = () => {
 return <h1>Hello, world</h1>;
};
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Step 1 — Understanding a Class without State or Lifecycle Methods ,Let’s take a look at class-based components with state and learn how to convert them to functional components using Hooks.,This code is an example of how you can convert a class-based React component with state to a functional component using Hooks.

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65%

Advantages of using functional components with hooks:,Life cycle methods that you would use in class components become simplified in functional components with the useEffect hook:,Once you understand the useState hook, the state in your functional component becomes easier to track and work with.

To make sure we’re on the same page, a functional component is just a function that returns JSX. Functional components can render differently based on the props you pass in:

const FunctionalComponent = (props) => {    return (<div> ... </div>);}

You’ll need to use hooks to do anything interesting with functional components. Hooks are nothing more than functions that are handled by React behind the scenes. They can handle managing state, listening for updates to state, and you can build custom ones. They tend to have a naming convention use*:

const FunctionalComponent = (props) => {    const [x, setX] = useState("Value for x");        return (<div> ... </div>); }

Initializing state in class components looks like this:

class SectionCard extends React.Component {
   constructor(props) {
      super(props);
      this.state = {
         title: "How to Article",
         content: "This is how you do"
      }
   }
}

You can consume the state later on in your render function (or lifecycle methods) like so:

class SectionCard extends React.Component {           constructor(props) {        super(props);        this.state = {            title: "How to Article",            content: "This is how you do"        }    }    render() {        return (            <div>                <h1>{this.state.title}</h1>                <p>{this.state.content}</p>            </div>        );    }}

You can update state in your component lifecycle methods (or in response to user input like a button clicking).

class SectionCard extends React.Component {           constructor(props) {        super(props);        this.state = {            title: "How to Article",            content: "This is how you do"        }    }   componentDidMount() {       this.setState({title: "Different title!"});   }   render() {       return (           <div>               <h1>{this.state.title}</h1>               <p>{this.state.content}</p>           </div>       );    }}

We use the useState hook for managing state. This hook takes an initial value of the state and spits out a reference and a setter method for the state value (common naming convention is x, setX):

const [x, setX] = useState("Initial string value X")

These useState hooks set the state for individual fields of our state:

const SectionCard = (props) => {
   const [title, setTitle] = useState("How to Article");
   const [content, setContent] = useState("This is how you do");...
}

To use these state fields, we include them when returning our JSX:

const SectionCard = (props) => {    const [title, setTitle] = useState("How to Article");    const [content, setContent] = useState("This is how you do");        ...    return (          <div>              <h1>{title}</h1>              <p>{content}</p>          </div>    );}

And when you want to set the state for either field, you simply use the setters:

const SectionCard = (props) => {    const [title, setTitle] = useState("How to Article");    const [content, setContent] = useState("This is how you do");    useEffect(() => { // Don't worry about useEffect right now       setTitle("Different Title");    }, []);    return (          <div>              <h1>{title}</h1>              <p>{content}</p>          </div>    );}

Life cycle methods that you would use in class components become simplified in functional components with the useEffect hook:

const FunctionalComponent = (props) => {    useEffect(() => {        ...    }, ...);    return (        <div>           ...        </div>    );}

useEffect takes a callback and an optional array of values it listens for. The callback will asynchronously fire if one of the values in that array change:

useEffect(() => {}, // Callback    [...] // Values this hook listens to);

Also, you can use multiple useEffect hooks if you want to have different callbacks called for different values changing:

const FunctionalComponent = (props) => {        useEffect(() => {        ...    }, [...]);    useEffect(() => {        ...    }, [...]);    return (        <div>           ...        </div>    );}
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The second type of component is the class component. Class components are ES6 classes that return JSX. Below, you see our same Welcome function, this time as a class component:,React has two types of components: functional and class. Let's look at each now in more detail.,We used to use class components because of "state". In the older versions of React (version < 16.8), it was not possible to use state inside functional components.

The first thing you'll realize after installing your first React project is that a JavaScript function returns some HTML code:

function App() {
  return (
    <div className="App">
      <header className="App-header">
        <img src={logo} className="App-logo" alt="logo" />
        <p>
          Edit <code>src/App.js</code> and save to reload.
        </p>
      </header>
    </div>
  );
}
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The core purpose of a React component is to define the displayed view and bind it to the code that drives its behavior. React’s functional components distill this down to the simplest possible profile: a function that receives properties and returns a JSX definition. Everything required for behavior is defined within the function body, and the class-related parts of object-oriented components are dropped.,The fundamental purpose of useEffect is to allow React’s render engine to reach inside component functions and initiate some action, to cause some effect.,Note that it is possible to define functional components with default return values, eliminating the return keyword via fat-arrow syntax as seen in Listing 4.

class QuipComponent extends React.Component {  render() {    return <p>What gets us into trouble is not what we don't know. It's what we know for sure that just ain't so.</p>;  }}<div id="app"></div>ReactDOM.render(<QuipComponent />, document.querySelector("#app"));
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Functional Components: Functional components are some of the more common components that will come across while working in React. These are simply JavaScript functions. We can create a functional component to React by writing a JavaScript function.,Make a counter app that will increase the number of counts as users click on the “Add” button using Functional and Class components.,Differences between Functional Components and Class Components in React

Syntax:

const Car=()=> {
  return <h2>Hi, I am also a Car!</h2>;
}

Syntax:

class Car extends React.Component {
  render() {
    return <h2>Hi, I am a Car!</h2>;
  }
}
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The difference between functional and class components,The reason for such a behavior lies in the essence of functional and class components. Let’s examine these lines of code:,So Hooks are more addition to functional components rather than a replacement of class components.

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