How can I parse a URL called between pages in a frameset?

Question

I have a 2-frame HTML page:

• FrameA contains a list of links to various pages, or anchors within pages
• FrameB displays the individual pages.

Some of the pages contain slideDown sections, with trigger text - i.e. clicking this text shows/hides the slideDown section below it.

The parent element of the trigger element also contains an anchor, for example:

<li class="expandable">
  <p><a name="myanchor3"></a>Trigger text</p>
  <div class="slideDownSection">
       ...
  </div>
</li>

I want to detect whenever an anchor is requested in the URL used to load the page into FrameB. If there is an anchor ref, I want to check whether the anchor falls within an "expandable" element and, if it is, I do a slideDown on the element below to display it.

I can do this easily enough by putting some Javascript inside a $(document).ready(function(){ ... }); in the page that gets loaded. This checks the location.hash value and processes it if one's found. However, this only works when the page gets loaded into FrameB.

If a page is already loaded into FrameB and I click a link in FrameA that points to another anchor within the same page, I can't capture that event. The page position changes to display the anchor at, or near, the top of the page - without reloading the page.

My question is:
What event handler can I use in the page displayed in FrameB to detect that an anchor on that page has been requested via a link clicked in FrameA?

Note: The content of FrameA is auto-generated, so I can't use an onClick event for the page in FrameA, I can only work within the pages that get displayed in FrameB.

Answer 1

IE8 supports the hashchange event that you can listen for. For all other browsers, you have to poll the value of location.hash using setInterval():

var lastHash = null;
function checkHash() {
  if (window.location.hash != lastHash) {
    lastHash = window.location.hash;

    // Do your hash stuff
  }
}

setInterval(checkHash, 100);

http://stackoverflow.com/questions/680785/on-window-location-hash-change is a very similar question.