Syntax
window.frames["frameName"].length
window.frames[num].length
The length property contains the number of frame instances in a document created with the tag.
<html>
<script language="JavaScript">
<!--
for(var i = 0; i <= window.frames.length; i++){
newWin.document.write("The name of frame #" + i);
newWin.document.write(" is " + window.frames[i].name + "<br>");
}
-->
</script>
</html>