index.js
index.html
 


import React from 'react';
import ReactDOM from 'react-dom';

class Header extends React.Component {
  constructor(props) {
    super(props);
    this.state = {favoritecolor: "red"};
  }
  static getDerivedStateFromProps(props, state) {
    return {favoritecolor: props.favcol };
  }
  changeColor = () => {
    this.setState({favoritecolor: "blue"});
  }
  render() {
    return (
      <div>
      <h1>My Favorite Color is {this.state.favoritecolor}</h1>
      <button type="button" onClick={this.changeColor}>Change color</button>
      </div>
    );
  }
}

ReactDOM.render(<Header favcol="yellow"/>, document.getElementById('root'));

/*
This example has a button that changes the favorite color to blue,
but since the getDerivedStateFromProps() method is called,
the favorite color is still rendered as yellow
(because the method updates the state
with the color from the favcol attribute).
*/
localhost:3000