function areEqual(prevProps, nextProps) {
return (prevProps.y.a.b===nextProps.y.a.b);}const Demo = React.memo(props=>{
console.log('rendering Demo');
return {props.y.a.b}
;},areEqual);class Example extends React.Component{
constructor(props){
super(props);
this.state={a:{b:0}};
}
componentDidMount(){
setInterval(()=>{
this.setState((state,props)=>({a:{b:0}}));
},1000);
}
render(){
console.log('rendering Example');
return ();
}}ReactDOM.render(,
document.querySelector('div'));