javascript实现的元素拖动函数宿主为浏览器

//宿主为浏览器  
//将相应的元素对象的引用传到函数中  
function candrag(drager) { 
  drager.onmousedown = function (down) { 
    var offx = drager.offsetLeft 
    var offy = drager.offsetTop; 
    var offxl = down.clientX - offx; 
    var offyl = down.clientY - offy; 
    window.condition = 0;//为window添加了condition属性，用于解决和click之间的矛盾  
    document.onmousemove = function (move) { 
      drager.style.left = move.clientX - offxl + "px"; 
      drager.style.top = move.clientY - offyl + "px"; 
      drager.style.cursor = "move"; 
      condition = Math.abs(move.clientX - down.clientX) + Math.abs(move.clientY - down.clientY); 
    } 
  } 
  drager.onmouseup = function () { 
    document.onmousemove = null; 
    draggerr.style.cursor = "auto"; 
  } 
}