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Apr 22

Overriding Core.JS functions

A client of mine recently required adding an additional E-Mail link adding to the Item Drop Down menu that drops off of the ECB menu within Document Libraries and Lists.

Now this functionality is provided by the function AddSendSubMenu(m,ctx) within Core.JS. Editing this file is NOT SUPPORTED (You all know this by now I’m sure!). So what to do? Well the answer is make use of Javascript’s natural override.. I.e. If you declare a function twice, the last declaration is the one that gets used.

So, Seems simple huh? We copy the function we want out of Core.JS and stick it into our own NewSendToMenu.js file in /TEMPLATE/LAYOUTS/1033

We then place a standard little script tag into the Head of the Master Page and bobs your uncle, the code gets loaded quite happily on each page.

Or does it? Well yes it does always get loaded.. I proved this by putting a document.write(“Hello World”) in front of the function and this got displayed every time without fail, And yet my customisations weren’t there.

I remembered reading somewhere that Core.JS has a habit of hanging around and getting executed last, My original method using the SharePoint:ScriptLink tag seemed to support this, so I dropped back to using the standard Script tags.. same problem though..

I then stumbled across a small article on the MSDN forums that pointed out the use of the Defer tag in the Core.JS script block. (You can see this if you view the page source in IE..) This means that the execution of Core.JS is deferred until the rest of the page is loaded, thus overriding my own override..

So the solution appears, Declare my script lower down the page than the Core.JS, and tag my Script block with the Defer option also.. This appears to execute my code AFTER core.js has completed.

Now, I’m not 100% how often this will be the case.. looks like this may need some load testing, but I think it’s fair to say that if one script is deferred higher up the page, than another lower down, they should be deferred into the same execution order that they met during page load?

Or am I being too simplistic? Never mind.. for now this works and resolves the client issue!

Paul

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