best reactjs tutorial code example

Example 1: react tutorial for beginners

class Board extends React.Component {
  constructor(props) {   
    super(props);  
    this.state = {   
      squares: Array(9).fill(null),
    }; 
  }
  renderSquare(i) {
    return <Square value={i} />;
  }
}

Example 2: react tutorial for beginners

import React from 'react';

class App extends React.Component {
   constructor(props) {
      super(props);
      
      this.state = {
         data: 'Initial data...'
      }
      this.updateState = this.updateState.bind(this);
   };
   updateState() {
      this.setState({data: 'Data updated...'})
   }
   render() {
      return (
         <div>
            <button onClick = {this.updateState}>CLICK</button>
            <h4>{this.state.data}</h4>
         </div>
      );
   }
}
export default App;