应该使用箭头函数，另外记得箭头函数中this指向定时器，所以在定时器之前用const that = this 在箭头函数中使用that指向vue

data() {
    return {
      uname: "",
      pwd: "",
      phone: "",
      code: "",
      sendMsg: "发送验证码",
      time: 60,
      disabled: false, //表示按钮是否禁用
      timer: "", //绑定定时器
    };
  },
  methods: {
    send() {
      if (!this.disabled) {
        this.sendMsg = this.time + "秒后重新发送";
        this.disabled = true;
        const that = this;
        this.timer = setInterval(() => {
          that.timeChange();
        }, 1000);
      }
    },
    timeChange() {
      //被定时器调用的函数
      this.time--;
      if (this.time <= 0) {
        clearInterval(this.timer);
        this.disabled = false;
      }
    },
    checkUp() {},
  },
  beforeDestroy() {
    this.disabled = false; //销毁时清除定时器
  },

另外记得在beforeDestroy中清除定时器

参考文章

vue 使用定时器setInterval，且解决不起作用_moon_watermelon的博客-CSDN博客_setinterval不起作用