vue计时器的实现方法

<div class="time" v-if="rptType">{{str}}</div>
<div class="receipt" :class="rptType?'jdz':'jiedan'" @click="receipt">开始</div>

data(){
 return{
  rptType: false,//状态
      h:0,//定义时，分，秒，毫秒并初始化为0；
        m:0,
        ms:0,
        s:0,
        time:0,
        str:'',
 }
},
mounted:function(){
 this.$nextTick(function () {//整个视图都渲染完毕
 })
},
methods:{
 getTask: function(e){
  this.taskType = e;
 },
 //开始
 receipt: function() {
  this.rptType = !this.rptType;
  if(this.rptType){
   this.time=setInterval(this.timer,50);
  }else{
   this.reset()
  }
 },
 timer: function(){   //定义计时函数
     this.ms=this.ms+50;         //毫秒
     if(this.ms>=1000){
       this.ms=0;
       this.s=this.s+1;         //秒
     }
     if(this.s>=60){
       this.s=0;
       this.m=this.m+1;        //分钟
     }
     if(this.m>=60){
       this.m=0;
       this.h=this.h+1;        //小时
     }
     this.str =this.toDub(this.h)+":"+this.toDub(this.m)+":"+this.toDub(this.s)+"";
     // document.getElementById('mytime').innerhtml=h+"时"+m+"分"+s+"秒"+ms+"毫秒";
 },
 toDub: function(n){  //补0操作
     if(n<10){
       return "0"+n;
     }
     else {
       return ""+n;
     }
 },
 reset: function(){  //重置
     clearInterval(this.time);
     this.h=0;
     this.m=0;
     this.ms=0;
     this.s=0;
     this.str="00:00:00";
 },
}