使用onmouseup设置元素位置到最近点不起作用

To leave out my application scenario for long story short, what I'd like to implement is something like jQuery Slider with anchor points split by equal interval. When I move the cursor and stop at an arbitrary position, there's a method called FindNearestAnchor triggered, and set the cursor position, and move it to the nearest anchor point.To leave out my application scenario for long s