vue获取验证码后倒计时

<span v-show="!this.timer" @click="getCode">获取验证码</span>
<span v-else class="count">{{count}} s</span>

data(){
  return {
   show: true,
   count: '',
   timer: null,
  }
 },
 methods:{
   getCode(){
     const TIME_COUNT = 60;
     if (!this.timer) {

　　　　// 发阿贾克斯请求
　　　　api.doSth
this.count = TIME_COUNT;
       this.show = false;
       this.timer = setInterval(() => {
       if (this.count > 0 && this.count <= TIME_COUNT) {
         this.count--;
        } else {
         this.show = true;
         clearInterval(this.timer);
         this.timer = null;
        }
       }, 1000)
      }
   }  
 }