Using "this" in JSP?

Question

<SELECT onchange="window.location.href=this.options
    [this.selectedIndex].value">
<OPTION VALUE="http://www.microsoft.com/ie">
    Internet Explorer</OPTION>
<OPTION VALUE="http://www.microsoft.com">
    Microsoft Home</OPTION>
<OPTION VALUE="http://msdn.microsoft.com">
    Developer Network</OPTION>
</SELECT>When I choose one of the options in this drop/down list I understand that "onchange" gets "fired".
I thought that selectedIndex took an argument corresponding to the option in the list (selectedIndex(2) is the second option in the drop/down-list). But here "this" is used in front of selectedIndex. Hope someone can explain.

Answer 1

Technically this is javascript and not java.
"this" refers to the event on which the object was fired. In this case it refers to the select object.
"selectedIndex" is an attribute of the select object, which tells it the index of the option which was selected.
http://msdn.microsoft.com/workshop/author/dhtml/reference/properties/selectedindex.asp
this.options gets you the list of options belonging to the select.
so
this.options[this.selectedIndex] is the actual selected option object.