【小程序】for循环中实现延时执行下一次 i++

需求：让用户感受到动态加载上图中的小点

    
for (var i = 0; i < spanNum; i++) {
      var color_i = "span[" + i +"].color";
      console.log(color_i);
      this.sleep(100);  //实现延时
      that.setData({
        [color_i]: '#4dcfff'
      })
      console.log(that.data.span[i].color)
      }



//延时
sleep:function(numberMillis) {
    var now = new Date();
    var exitTime = now.getTime() + numberMillis;
    while(true) {
      now = new Date();
      if (now.getTime() > exitTime)
        return;
    }
  }