function parabola(ele, stop){                  //y == a*x^2 + bx + c         //原点         var centerpoint = {             x : ele.offsetLeft,             y : ele.offsetTop         }         //目标点的 相对坐标系位置         var target = {             x : stop.offsetLeft - centerpoint.x,             y : centerpoint.y - stop.offsetTop         }         //系数         var a = -0.0015;         // b = (y - ax^2)/x         b = (target.y - a*target.x*target.x)/target.x;                  var _x = 0;         var t = setInterval(function(){             _x+=8;             var _y = a*_x*_x + b*_x;             ele.style.left = _x + centerpoint.x + "px";             ele.style.top = centerpoint.y - _y + "px";                          if(_x >= target.x) {                 ele.style.left = stop.offsetLeft + "px";                 ele.style.top = stop.offsetTop + "px";                 clearInterval(t)             }         }, 20);     }
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