这有点奇怪。我一直试图从父对象调用子对象中的函数，但它似乎超出了onbeforenload函数的范围。这些函数调用在onbeforeunload之外工作，因此只有在onbeforunload中调用时才会失败。我可以通过将子对象设置为全局对象来解决这个问题，但我试图避免这种情况。有人知道为什么我的子对象在onbeforeunload中调用时超出范围吗？请注意，我在windows onload事件中调用了相同的函数，它运行良好。这是代码：
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Broken HTA</title>
<HTA:APPLICATION
ID="Broken HTA"
APPLICATIONNAME="Broken HTA"
BORDERSTYLE = "flat"
CAPTION="Yes"
CONTEXTMENU = "no"
INNERBORDER = "no"
MAXIMIZEBUTTON = "no"
MINIMIZEBUTTON = "yes"
NAVIGABLE = "No"
SCROLL = "auto"
SCROLL FLAT = "Yes"
SELECTION="no"
SYSMENU="yes"
SHOWINTASKBAR="yes"
SINGLEINSTANCE="yes"
VERSION = "1.0"
BORDER="thick"
>
<script language="javascript" type="text/javascript">
var myparent;
function windowLaunch()
{
myparent = new parent();
myparent.getchildvalue();
window.onbeforeunload = myparent.getchildvalue;
window.resizeTo(500, 610);
}
function parent()
{
this.mychild = new childobject("myinput");
this.getchildvalue = function()
{
var tmpval = this.mychild.returnvalue();
};
}
function childobject(thename)
{
this.myprop = thename;
this.returnvalue = function()
{
return (document.getElementById(this.myprop).value);
};
}
</script>
</head>
<body id="thebody" onload="windowLaunch();">
<div id="outerdiv">
<span title="This Input Box">My Input:</span><br />
<input id="myinput" style="width: 290px"/>
</div>
</body>
</html>
this基于函数的调用方式。调用myparent.getchildvalue()是可以的，但一旦将myparent.getchildvalue指定为处理程序，就会在上下文之外调用。你可以简单地证明这一点：
var obj = { val: 42, fn: function(){ alert(this.val) } };
ref = obj.fn;
alert(obj.fn === ref); // true, so expect the following to do the same thing...
obj.fn(); // 42, so far so good
ref(); // undefined. uh oh...
你可以通过包装来解决这个问题：
...
window.onbeforeunload = function(){ myparent.getchildvalue(); };
...
或绑定：
...
window.onbeforeunload = myparent.getchildvalue.bind(myparent);
...