'overriding' javascript function

Question

I need to add some validations before the user navigates away via an ASP.NET Menu.

I noticed that the items are rendered to use a javascript function called Menu_Key

<td id="ctl00_MainMenun1" onmouseover="Menu_HoverStatic(this)" onmouseout="Menu_Unhover(this)" onkeyup="Menu_Key(this)">

I there a way to override that function and have the menu execute one of mine, from which I could validate what I need and then call the original?

Answer 1

Redefine the function after it was initially defined, but keep track of it in a var so that you can call it later. You would effectively be renaming the original Menu_Key function.

var originalMenu_Key = Menu_Key;

Menu_Key = function(t) { 
   // do your validations here

   if ( /* everything validated */ ) {
     originalMenu_Key (t);
   }
};