javascript - 如何在 mousedown 时保持鼠标指针位置

Question

鼠标指针位置是否可以在mousedown时冻结，我觉得这会限制抓取和鼠标离开可抓取区域的问题，我在许多其他游戏等中多次看到此功能希望阅读此内容的你理解我建议的功能类型...

这是我的代码。如果有人修复了鼠标冻结，请随时更新它...

var container=document.getElementById('container');
 bottom =3750;
 rightside = 1300 ;
 leftside = 0,
 topside=0;

 var selected = null, // Object of the element to be moved
 x_pos = 0, y_pos = 0, // Stores x & y coordinates of the mouse pointer
 x_elem = 0, y_elem = 0; // Stores top, left values (edge) of the element

// Will be called when user starts dragging an element
function _drag_init(elem) {
// Store the object of the element which needs to be moved
   selected = elem;
   x_elem = x_pos - selected.offsetLeft;
   y_elem = y_pos - selected.offsetTop;     
}

// Will be called when user dragging an element
function _move_elem(e) {
   x_pos = document.all ? window.event.clientX : e.pageX;
   y_pos = document.all ? window.event.clientY : e.pageY;

    if (x_pos-x_elem <=leftside){
       x_pos =leftside + x_elem;
    }

    if (x_pos >=rightside){
       x_pos =rightside-10;
    }

    if (y_pos-10 <=topside){ 
       y_pos=topside+10;
    }

    if (y_pos+380 >=bottom){ 
       y_pos=bottom-380;
    }

    if (selected !== null) {
       selected.style.left = (x_pos - x_elem) + 'px';
       selected.style.top = (y_pos - y_elem) + 'px';
    }   
}

// Destroy the object when we are done
function _destroy() {
    selected = null;
}

// Bind the functions...
  document.getElementById('frame1').onmousedown = function () {
  _drag_init(this);
  return false;
};

document.onmousemove = _move_elem;
document.onmouseup = _destroy;