Why is "window.location instanceof Location" false in IE?

I'm working on a jQuery plugin which maps URL anchors to JS functions. The plugin takes an argument which either can be a DOM element or a Location object. So I need a way to check what kind a given argument is.

I tested the following code in FF 3.6 and IE 8. The former alerts true, the latter alerts false. Why is this and how can I accomplish the same behavior in both browsers? Thank you!

<!DOCTYPE html>
<html>
    <head>
        <script>
            alert(window.location instanceof Location);
        </script>
    </head>
    <body>
    </body>
</html>

Solution

EDIT: With regard to the comment under your question, it sounds like you need to test for the difference between a DOM element, and a Location object.

You'll probably be better off testing for the DOM element using the nodeType property.

if( obj.nodeType ) {
    // it was a DOM element
}

Then you can test for various properties if nodeType wasn't found, just to be certain it is a location object.

if( obj.nodeType ) {
    // it was a DOM element
} else if( obj.hostname && obj.pathname ) {
    // it was a location object
} else {
    // some ERROR
}

Original answer:

This works for me in Chrome, Safari, Firefox:

Object.prototype.toString.call(window.location) == '[object Location]';

I can't test in IE right this minute, though.

This is the method noted in the ECMAScript spec Section 8.6.2 for getting the internal [[Class]] property name.