Jquery .animate（）...返回错误的偏移量;

Question

在下面的代码中，如果其中一个条件为true并运行animate代码，为什么console.log都返回相同的值（偏移量）？

$(document).on("click",".box",function(){
            var transparent = $("#transparent");
            var transparent_left = transparent.offset().left;
            var transparent_top = transparent.offset().top;
            var box = $(this);
            var this_top = box.offset().top;
            var this_left = box.offset().left;
            console.log(this_top +" "+this_left);

            if(transparent_top === (this_top + 100)
            && transparent_left === this_left){ 
                box.finish().animate({top: "+=100"});
                transparent.finish().animate({top: "-=100"});
            }else if(transparent_top === this_top
            && transparent_left === (this_left + 100)){ 
                box.finish().animate({left: "+=100"});
                transparent.finish().animate({left: "-=100"});
            }else if(transparent_top === this_top 
            && (transparent_left + 100) === this_left){ 
                box.finish().animate({left: "-=100"});
                transparent.finish().animate({left: "+=100"});
            }else if((transparent_top + 100) === this_top
            && transparent_left === this_left){ 
                box.finish().animate({top: "-=100"});
                transparent.finish().animate({top: "+=100"});
            }

            this_top = box.offset().top;
            this_left = box.offset().left;
            console.log(this_top +" "+this_left);

        });