ResolveUrl in Javascript

This is something that is super easy, yet I get asked about it quite often.

Here’s how you do it:

In the master page for the site, put this:

<script type="text/javascript">
        var baseUrl = "<%= ResolveUrl("~/") %>";
</script>

Then, in your javascript file, put this function:

function ResolveUrl(url) {
    if (url.indexOf("~/") == 0) {
        url = baseUrl + url.substring(2);
    }
    return url;
}

You could have put the function right in the master page, but then you wouldn’t get intelli-sense on it for the rest of your code.

Now you can call ResolveUrl with ~/ right from javascript. 

Super easy, but also super useful!

If you use themes, you might even want to write something that does a “get themed url” where the current theme is output from the master page via Page.Theme.

more later – joel.