What is a React Class Component?

About

A React Class component is a React component created via a Javascript.

Even if class component are now an old technology, they are still used and are also still mandatory knowledge if you want to create an Error boundary (ie catch all error component)

Syntax

Javascript

class Welcome extends React.Component {

   // Optional. Needed to set state
  constructor(props) {
     super(props); // Always call the base constructor with props.
  }
  
  render() {
    return <h1>Hello, {this.props.name}</h1>;
  }
  
}

Feature available only to classes:

Local state
Lifecycle function.

Typescript

type MyProps = {
  name: string,
  children: React.ReactNode
}

class Welcome extends React.Component<MyProps> {

   // Optional. Needed to set state
  constructor(props:MyProps) {
     super(props); // Always call the base constructor with props.
     this.state = ...
  }
  
  render() {
    return (
      <>
       <h1>Hello, {this.props.name}</h1>
       {children}
      </>
     );
  }
  
}