# 定时器问题

react 组件里使用定时器时得注意清除定时器，否则组件在卸载的时候，定时器还在运行。定时器开启和清除的地方

```javascript
componentDidMount(){

    this.timeID = setTimeout(function(

            console.log(222)
      ){},200)

}


componentWillUnmount(){


    clearTimeout(this.timeID);


}
```


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