Get started with ReactJS: A Beginner’s Guide

What is React?

React is a JavaScript library for creating user interfaces. It is maintained by Facebook and a community of individual developers and companies. React can be used as a base in the development of single-page or mobile applications.

React allows developers to build large web applications that can change data without having to reload the page. React aims to provide a way to rapidly build web applications that are scalable.

React is a JavaScript library for creating user interfaces.

benefits of feedback

React is known for its speed, scalability and simplicity. The main advantage of React is its performance.

React is capable of handling large amounts of data quickly and efficiently. This makes React a good choice for developing large scale applications.

Its declarative syntax makes code easy to read and maintain, while its virtual DOM ensures fast performance. React is also suitable for large applications with complex data structures.

Here are some other benefits of React that make it a great choice for web development:

  • JSX makes creating templates easier and more concise

  • It lets you create reusable components so that your code is easier to read and maintain.

  • React JS is advantageous because of its simplicity, flexibility and scalability.

  • Additionally, working with the ReactJS framework helps improve team collaboration and communication.

  • React can be used to build single-page applications.

  • It’s declarative: React makes it painless to build interactive UIs. Design simple views for each state in your application, and when your data changes, React will efficiently update and render the correct components.

react jsx

React is unique because it uses a declarative paradigm and a JavaScript syntax extension called JSX. It makes the code more readable and helps to ease development.

JSX is a syntax extension for React that allows you to write markup directly in your JavaScript code.

const myElement = <h1>I Love JSX!</h1>;

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(myElement);
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Without JSX:

const myElement = React.createElement('h1', {}, 'I do not use JSX!');

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(myElement);
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JSX is an XML-like syntax extension for ECMAScript without any defined semantics. It is not intended to be implemented by the engine or browser.

This is not a specification. It is intended to be used by various preprocessors (transpilers) to convert these tokens into standard ECMAScript.

JSX is a syntax extension to JavaScript that lets you write HTML-like syntax within your JavaScript code. With React, you can use either regular JavaScript or JSX.

react component

react class component

React class components are one of the ways you can create React components. They are created by extending the React.Component class.

In a react class component, you will need to create a render() method. The render() method will return a response element.

When creating a class component, you need to extend the React.Component class. It gives your component the ability to have state and lifecycle methods.

The components of the class are also easier to test, as they are just JavaScript classes. They allow you to use JavaScript classes to create React components.

Class components are more powerful than functional components and can have state. They make it easy to create reusable code, and they are great for working with large applications.

React introduced official support for class components in version 15.5. Class Components are a more traditional way of writing React components using a class. They can be used with React’s new context API and static getDerivedStateFromProps lifecycle methods.

Class components should be used when you need to use one of these attributes or other capabilities unique to the class, such as access to local state or lifecycle methods.

class Welcome extends React.Component {
  render() {
    return <h1>Hello, {this.props.name}</h1>;
  }
}
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react function component

Function components are an easy way to write React components. They are equivalent to stateless functional components in React.

Simply put, function components are functions that return React elements. When you need a component that doesn’t have state, you can use the Function component.

A Function component is a simple functional unit used to create React components. It accepts props and returns a response element.

When you create a React component, you have the option of creating a function component or a class component.

A Function component is a React component that is written as a JavaScript function.

Function components are simpler than class components, and are often used for presentational components.

function Welcome(props) {
  return <h1>Hello, {props.name}</h1>;
}
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Feedback props

React Props provides a way for the parent component to pass data to the child component. The child component can access that data through the this.props object.

React props are also used to specify the behavior of a component, such as whether it should be rendered or not.

React props are pieces of data that are passed to React components. They are used to customize the behavior of a component, and they can be used in conjunction with state to manage data within a component.

React props are immutable, which means they cannot be changed once set.

This makes them perfect for passing data down the component tree, and it helps to keep your components modular and easy to reason about.

function Person(props) {
  return <h2>I'm { props.name }!</h2>;
}

function Greeting() {
  const name = "Jesse"
  return (
    <>
      <h1>Hello!</h1>
      <Person name=
{
 name 
}
 />
    </>
  );
}

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(<Greeting />);
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response state

React State is one of the most important concepts in React.
It refers to the data that a React component needs in order to render itself.

create state object

The state object is initialized in the constructor:

class Car extends React.Component {
  constructor(props) {
    super(props);
    this.state = {brand: "Ford"};
  }
  render() {
    return (
      <div>
        <h1>My Car</h1>
      </div>
    );
  }
}
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React State can be used to store the data that a component needs to render itself.

When a component’s state changes, the component will re-render itself. There are two ways to change the state of a component: setState and forceUpdate.

class Car extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      brand: "Ford",
      model: "Mustang",
      color: "red",
      year: 1964
    };
  }
  changeColor = () => {
    this.setState({color: "blue"});
  }
  render() {
    return (
      <div>
        <h1>My {this.state.brand}</h1>
        <p>
          It is a {this.state.color}
          {this.state.model}
          from {this.state.year}.
        </p>
        <button
          type="button"
          onClick={this.changeColor}
        >Change color</button>
      </div>
    );
  }
}
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React setState is a function used to update the state of a React component. The function takes two arguments, the first is an object containing the new state values ​​and the second is a callback function.
The callback function is executed after the new state value is applied. The new state values ​​are merged with the previous state values.

React ForceUpdate is a function that causes a component to be rerendered.
This can be useful if you need to make changes to a prop or position that will cause a component to look different.
ForceUpdate will not call shouldComponentUpdate so it is not suitable for all situations. Use it sparingly!

class App extends React.Component {  
constructor() {  
super();        
this.state = {  
message: "Hello World"  
};      
this.updateSetState = this.updateSetState.bind(this);  
}  
updateSetState() {  
this.setState({  
message:"It is a beautiful day."  
});  
}  
render() {  
return (  
<div>  
<h1>{this.state.message}</h1>  
<button onClick = {this.updateSetState}>SET</button>  
</div>  
);  
}  
}  
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In the example above, the data displayed is updated from “Hello World” to “It’s a Beautiful Day”. click the button

When a developer wants to update a view in React, they call the forceUpdate function. This function tells React that the component needs to be rerendered.

When the forceUpdate function is called, React will re-render the component even if the component’s prop or position has not changed.
The forceUpdate function is used when a change occurs outside of the component, such as an event listener firing or a request from an API returning data.

React State is a powerful concept that allows developers to easily manage data within their React applications.

Using state, developers can build complex applications that are responsive to user input and can change over time.

React State is easy to use and can be a great way to improve the performance of your application.

render a react component

To display a React component, you must first “render” the component. It simply means that you have to output the correct HTML code from your React component so that it can be displayed in the browser.

The process of rendering a React component is actually quite simple. First, you create a new React element. This element can be either a DOM element or a custom React component.

<div id="root"></div>
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Once you have created your element, you use ReactDOM. This library will allow you to render your React component in an HTML element on the page.

const root = ReactDOM.createRoot(
  document.getElementById('root')
);
const element = <h1>Hello, world</h1>;
root.render(element);
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Once you’ve rendered your component, you can interact with it using the ReactDOM API.

Updating rendered React components

In the past, when a React component was provided, it was static. Once rendered, the component could not be changed.

This made it difficult to update components that needed to change based on user interaction or new data.

However, there is now a way to update a rendered React component. Using the setState method, a developer can change the component after it has been rendered.

It makes it possible to create dynamic and interactive user interfaces with React.

When building an application with React, it is important to be able to update the rendered component.

There are two ways to do this: with component position or props. Updating a component’s state will re-render the component, and updating a component’s props will update the component.


class App extends Component {
constructor(props){
    super(props)

    // Set initial state
    this.state = {greeting :
        'Click the button to receive greetings'}

    // Binding this keyword
    this.updateState = this.updateState.bind(this)
}

updateState(){
    // Changing state
    this.setState({greeting :
                'GeeksForGeeks welcomes you !!'})
}

render(){
    return (
    <div>
    <h2>Greetings Portal</h2>
    <p>{this.state.greeting}</p>

        {/* Set click handler */}
        <button onClick={this.updateState}>
        Click me!
        </button>
    </div>
    )
}
}

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To update a rendered React component, you must use the setState method. This method will take in the object that contains the new data you want to update the component.

Once you have updated the state of the component, the component will re-render with the new data. If you need to make api call to fetch new data, you can do it inside setState method.

conclusion

In conclusion, ReactJS is a great tool for building user interfaces. It is fast, efficient and easy to learn. If you’re looking for a way to get started with ReactJS, this guide is a great place to start.

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