javascript 的点击复制事件

function copy()
{
    var text=document.getElementById("txtUser").value;
    if(copy2Clipboard(text)!=false)
    {
        alert("复制成功了！ ");
    }
}
function copy2Clipboard(txt)
{
    if(window.clipboardData)
    {
        window.clipboardData.clearData();
        window.clipboardData.setData("Text",txt);
    }else if(navigator.userAgent.indexOf("Opera")!=-1){
        window.location=txt;
    }else if(window.netscape)
    {
        try
        {
            netscape.security.PrivilegeManager.enablePrivilege("UniversalXPConnect");
        }
        catch(e){
            alert("您使用的浏览器不支持此复制功能，请使用Ctrl+C或鼠标右键。");
            return false;
        }
        var clip=Components.classes['@mozilla.org/widget/clipboard;1'].createInstance(Components.interfaces.nsIClipboard);
        if(!clip)return;
        var trans=Components.classes['@mozilla.org/widget/transferable;1'].createInstance(Components.interfaces.nsITransferable);
        if(!trans)return;
        trans.addDataFlavor('text/unicode');
        var str=new Object();
        var len=new Object();
        var str=Components.classes["@mozilla.org/supports-string;1"].createInstance(Components.interfaces.nsISupportsString);
        var copytext=txt;str.data=copytext;
        trans.setTransferData("text/unicode",str,copytext.length*2);
        var clipid=Components.interfaces.nsIClipboard;
        if(!clip)return false;
        clip.setData(trans,null,clipid.kGlobalClipboard);
        return true;
    }
}