利用JS实现数字增长

this.fomatNum = function(num) {      var str = num.toFixed(this.option.decimal);//精确到小数位数多少位      var num1, x1, x2, reg;      arr = str.split(".");      x1 = arr[0];      x2 = arr.length > 1 ? '.' + arr[1] : "";      reg = /(/d+)(/d{3})/;      if (this.option.isfomat) {        while (reg.test(x1)) {          x1 = x1.replace(reg, '$1' + "," + "$2");        }      }      if (this.option.isfomat) {        return this.option.prefix + x1 + x2;      } else {        return this.option.prefix + str;      }    }

var change = function() {  var p = Math.min(1.0, (new Date().getTime() - that.startTime) / that.option.duration);//当前时间减去开始时间，然后除以总时间，Math.min,两个数取最小值。  var nums = that.num * p;  that.elm.innerHTML = that.fomatNum(that.num * p);  if (p < 1.0) {//     requestAnimationFrame(function() {        change();     });   } else {        cancelAnimationFrame(change);       }  }  requestAnimationFrame(function() {     change();   });