javascript - React, React-Router and setInterval -


i have component state wish regularly update timing function, therefore have following code:

componentdidmount() {      console.log("stage.componentdidmount")      // var self = this;     if (this.timer == null) {         console.log("create timer")          var timerfunction = function() {             console.log(this.timer);         }.bind(this)          this.timer = setinterval(timerfunction, 1000);       } }  componentwillunmount() {     console.log("component unmount")     clearinterval(this.timer) }

the problem comes in when refresh route subcomponent subcomponent. notice parent of component renders twice, , therefore components constructor , componentdidmount called twice. creates 2 timers, , timing invocations of twice numerous!

while isn't problem when navigating route , navigating away, componentdidmount , componentwillunmount calls balance each other out, problem when refreshing reason described.

is there sort of balancing function or way prevent route's subcomponent (the 1 creating timer in componentdidmount shown in code sample) creating more 1 timer?

here root file, setups of routing , renders "renderer" contains subcomponent constructor called twice.

import react 'react'; import reactdom 'react-dom'; import {browserrouter router, route } 'react-router-dom' import './styles.css';  const navlink = require( 'react-router-dom' ).navlink  import renderer './renderer/renderer' import rootcomponent './componentsscratchpad/rootcomponent'  function nav() {             return (             <ul classname='nav'>             <li><navlink activeclassname="active" exact to='/componentsscratchpad'>scratch pad</navlink></li>             <li><navlink activeclassname="active" exact to='/renderer'>renderer</navlink></li>             </ul>             )  }   class app extends react.component {      render() {         return (             <router>             <div>             <nav />             <route exact path='/renderer' render={ () => <renderer /> } />             <route exact path="/componentsscratchpad" render={ () => <rootcomponent /> }/>             </div>             </router>             )     } }  reactdom.render(<app />, document.getelementbyid('root'))


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