利用canvas实现的加载动画效果实例代码

/*核心代码*/
/*分析动画，其实动画只有两次的执行*/
   var for_index = 1;//记录当前执行动画的序列
   var interval = setInterval(function(){
    if(for_index == 1){
     if(squre4.x == origin_squre.x - step * 2){
      for_index = 2;
     }else{
      squre2.x -= 2;
      squre2.y += 1;

      squre4.x += 2;
      squre4.y -= 1;
     }
    }else if(for_index == 2){
     if(squre4.x == origin_squre.x){
      for_index = 1;

      /*重置方块位置信息到初始值*/
      init_squre(origin_squre.x,origin_squre.y);

     }else{
      squre3.x -= 2;
      squre3.y -= 1;

      squre2.x -= 2;
      squre2.y -= 1;

      squre4.x += 2;
      squre4.y += 1;

      squre1.x += 2;
      squre1.y += 1;
     }
    }
    ctx.clearRect(0,0,canvas.width,canvas.height);
    /*重绘方块*/
    if(for_index == 1 || for_index == 2){
     draw_squre(squre4);
     draw_squre(squre1);
     draw_squre(squre3);
     draw_squre(squre2);
    }

    /*重绘阴影*/
    get_shaow_pos();
    for(var i in shaow_begin){
     draw_shaow(shaow_begin[i]);
    }
   },1000 / 24);