If iframe object would have been a window object, it would have had accepted all the usual window methods, which is far from true. AFAIK it suppports only onload window's event.
This demo page will speak for itself. It dumps the methods, properties and event handlers of IFRAME accessed in 3 different ways. Try it.
<html>
<head>
<title>Supported methods and properties of IFRAME</title>
<style type="text/css">
td, th {vertical-align:top;padding:2px;}
body,table {font:11px Verdana;}
#note {font-style:italic;color:red;}
</style>
<script type="text/javascript">
function dumpIframe(oIframe, contentId){
var str="";
for (var item in oIframe){
if (typeof oIframe[item] == "function")
str += "<b>" + item + "</b> = [function]<br />"; //for Firefox
else if (item.indexOf("on") == 0)
str += "<b>" + item + "</b> = [event handler]<br />"; //for IE
else
str += "<b>" + item + "</b> = " + oIframe[item] + "<br />";
}
document.getElementById(contentId).innerHTML = str;
}
function init(){
dumpIframe(window.frames['ifrName'], 'column1'); //via frames collection
dumpIframe(document.getElementById('ifrId').contentWindow, 'column2'); //via document.getElementById(...).contentWindow
dumpIframe(document.getElementById('ifrId'), 'column3'); //via document.getElementById(...)
}
window.onload = init;
</script>
</head>
<body>
<iframe name="ifrName" id="ifrId" src="about:blank"></iframe>
<h1>Supported methods and properties of IFRAME</h1>
<table border="1" cellpadding="0" cellspacing="0">
<tr>
<th>via frames[ ] collection</h>
<th>document.getElementById(...).contentWindow</h>
<th>document.getElementById(...)</h>
</tr>
<tr>
<td style="width:33%">
<div id="column1"></div>
</td>
<td style="width:33%">
<div id="column2"></div>
</td>
<td style="width:34%">
<div id="column3"></div>
</td>
</tr>
</table>
<div id="note">
*NOTE: IE doesn't dump methods while Firefox does. IE dumps event handlers while Firefox doesn't.
But of course, methods and event handlers are supported by both browsers.
</div>
</body>
</html>