javascript - Update React component every second

Question

I have been playing around with React and have the following time component that just renders Date.now() to the screen:

import React, { Component } from 'react';

class TimeComponent extends Component {
  constructor(props){
    super(props);
    this.state = { time: Date.now() };
  }
  render(){
    return(
      <div> { this.state.time } </div>
    );
  }
  componentDidMount() {
    console.log("TimeComponent Mounted...")
  }
}

export default TimeComponent;

What would be the best way to get this component to update every second to re-draw the time from a React perspective?

Answer 1

You need to use setInterval to trigger the change, but you also need to clear the timer when the component unmounts to prevent it leaving errors and leaking memory:

componentDidMount() {
  this.interval = setInterval(() => this.setState({ time: Date.now() }), 1000);
}
componentWillUnmount() {
  clearInterval(this.interval);
}