class Demo extends React.PureComponent {
constructor(props) {super(props);}
render() {
console.log('rendering Demo');
return
Testing
;
}}class Example extends React.Component{
constructor(props){
super(props);
this.state={a:0};
}
componentDidMount(){
setInterval(()=>{
this.setState((state,props)=>({a:state.a+1}));
},1000);
}
render(){
console.log('rendering Example');
return ();
}}ReactDOM.render(
,
document.querySelector('div'));