捕获鼠标事件拖动的js代码 拖动窗口

HTML-body：

JavaScript：
function drag(target,event){ var startX = event.clientX; var startY =
event.clientY;

    var origX = target.offsetLeft; var origY = target.offsetTop;

    var deltaX = startX - origX; var deltaY = startY - origY;

    target.setCapture();

    target.attachEvent("onmousemove",moveHandler);

    target.attachEvent("onmouseup",upHandler);

    target.attachEvent("onlosecapture",upHandler);

    event.cancelBubble = true; event.returnValue = false;

    function moveHandler(){ var evt = window.event;

        target.style.left = (evt.clientX- deltaX)+"px";

        target.style.top = (evt.clientY- deltaY)+"px";

        evt.cancelBubble = true; }

    function upHandler(){ var evt = window.event;

        target.detachEvent("onlosecapture",upHandler); 
        target.detachEvent("onmouseup",upHandler); 
        target.detachEvent("onmousemove",upHandler);

        target.releaseCapture();

        evt.cancelBubble = true; } }

这是一个捕获鼠标事件拖动的js代码，为什么语法错误？

 attachEvent 有浏览器兼容性问题
 IE11不支持，firefox不支持
 判断一下
 if (window.attachEvent) { 
                window.attachEvent("onmousemove", remove); 
            } else if (window.addEventListener) { 
                window.addEventListener("onmousemove", remove, false);   
            }