小程序验证码倒计时不会开始，下面是代码 ，帮我看一下

// 倒计时
  countDown() {
    //倒计时
    let time = 60;
    let timer = setInterval(() => {
      if (time == 0) {
        clearInterval(timer);
        var codetext = '获取验证码';
        this.setData({
          disabled: false,
          codetext: codetext,
        })
      } else {
        this.setData({
          disabled: false,
          codetext: time + '秒',
        })
        time--
      }
    }, 1000)
  },