vue 타이머 구현 방법

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

data(){
 return{
  rptType: false,//  
      h:0,//   ， ， ，       0；
        m:0,
        ms:0,
        s:0,
        time:0,
        str:'',
 }
},
mounted:function(){
 this.$nextTick(function () {//         
 })
},
methods:{
 getTask: function(e){
  this.taskType = e;
 },
 //  
 receipt: function() {
  this.rptType = !this.rptType;
  if(this.rptType){
   this.time=setInterval(this.timer,50);
  }else{
   this.reset()
  }
 },
 timer: function(){   //      
     this.ms=this.ms+50;         //  
     if(this.ms>=1000){
       this.ms=0;
       this.s=this.s+1;         // 
     }
     if(this.s>=60){
       this.s=0;
       this.m=this.m+1;        //  
     }
     if(this.m>=60){
       this.m=0;
       this.h=this.h+1;        //  
     }
     this.str =this.toDub(this.h)+":"+this.toDub(this.m)+":"+this.toDub(this.s)+""/*+this.toDubms(this.ms)+"  "*/;
     // document.getElementById('mytime').innerHTML=h+" "+m+" "+s+" "+ms+"  ";
 },
 toDub: function(n){  // 0  
     if(n<10){
       return "0"+n;
     }
     else {
       return ""+n;
     }
 },
 reset: function(){  //  
     clearInterval(this.time);
     this.h=0;
     this.m=0;
     this.ms=0;
     this.s=0;
     this.str="00:00:00";
 },
}