shouldComponentUpdate

shouldcomponentupdate.jsx

import React from 'react';

export class Example extends React.Component {
  constructor(props) {
    super(props);

    this.state = { subtext: 'Put me in an <h2> please.' };
  }

  shouldComponentUpdate(nextProps, nextState) {
    if ((this.props.text == nextProps.text) && 
      (this.state.subtext == nextState.subtext)) {
      alert("Props and state haven't changed, so I'm not gonna update!");
      return false;
    } else {
      alert("Okay fine I will update.")
      return true;
    }
  }

  render() {
    return (
      <div>
        <h1>{this.props.text}</h1>
        <h2>{this.state.subtext}</h2>
      </div>
    );
  }
}