const timer = {
        time: 0,
        start: function () {
          // this
          // var self = this;
          var that = this;
          btn.addEventListener(
            'click',
            function () {
            // 老师这里设表先关不起作用
              var t;
              clearInterval(t);
              t=setInterval(function () {
                console.log(this);  //window
                console.log(that);  // timer对象
                // this.time++;
                // result.innerHTML = this.time;
                that.time++;
                result.innerHTML = that.time;
              }, 1000);
            },
            false
          );
        }
      };
      
 timer.start();