Reader Kevin posed a good question in response to my last post, the answer to which is useful enough to warrant a separate post:

I have a situation where I call a page load handler from a script associated with a master page, then on a specific page based on that master page I need to call a second page load handler. I use the pageLoad() shortcut notation in the master page script. I can’t get either pageLoad() (expected since the composite page would have two pageLoad’s) or $addHandler(document, “load”, mySpecificPageLoad()) to work. I had to resort to my old “addLoadListener” function to add the second page load event handler. Is this as expected?

As he mentions, there’s only room in the page’s DOM for one pageLoad shortcut function, preventing both a master and content page from utilizing the shortcut simultaneously.

To work around this limitation, simply add this to your master’s pageLoad:

<script type="text/javascript">
  function pageLoad() {
    // Master pageLoad() code.
 
    // If function contentPageLoad exists, execute it.
    if(typeof contentPageLoad == 'function')
      contentPageLoad();
}

Now, contentPageLoad is executed on any content page you wish to include it on, just as if it were pageLoad. If you don’t include it on a particular content page, the conditional will prevent its execution (and subsequent JavaScript error).

You could use Sys.Application.add_Load to wire up a custom pageLoad on every single content page, but I think the DRY-ness of this approach is preferable. The above method also allows you to retain control of the order of execution, through the placement of the contentPageLoad call in pageLoad.