component will update react code example

Example 1: componentDidUpdate

componentDidUpdate(prevProps, prevState) {
  if (prevState.pokemons !== this.state.pokemons) {
    console.log('pokemons state has changed.')
  }
}

Example 2: lifecycles if reactjs

class Clock extends React.Component {
  constructor(props) {
    super(props);
    this.state = {date: new Date()};
  }

  componentDidMount() {  }
  componentWillUnmount() {  }
  render() {
    return (
      <div>
        <h1>Hello, world!</h1>
        <h2>It is {this.state.date.toLocaleTimeString()}.</h2>
      </div>
    );
  }
}

Example 3: component did mmount

componentDidMount()

Example 4: react lifecycle

constructor(props) {
  super(props);
  // Don't call this.setState() here!
  this.state = { counter: 0 };
  this.handleClick = this.handleClick.bind(this);
}