JAVASCRIPT

set interval react

useEffect(() => {
  const interval = setInterval(() => {
    console.log('This will run every second!');
  }, 1000);
  return () => clearInterval(interval);
}, []);

set interval react

timer: function() {
   var newCount = this.state.currentCount - 1;
   if(newCount >= 0) { 
       this.setState({ currentCount: newCount });
   } else {
       clearInterval(this.state.intervalId);
   }
},

react using set Interval date time

const render = () => {
document.getElementById('mountNode').innerHTML=
  `
<div>
  Hello HTML
  <input />
  <pre>${(new Date).toLocaleTimeString()}</pre>
    </div>`;



ReactDOM.render(
React.createElement('div',null,'Hellow World',
  React.createElement('input',null),
    React.createElement('pre',null,(new Date).toLocaleTimeString())
),
document.getElementById('mountNode2')
  );
};
setInterval(render, 1000)