I spent a decent amount of time trying to workaround not being able to access the body onload event of a SharePoint page, including looking at adding JavaScript event handlers programatically, before I came across this… almost an aside in another article.
In order to work around this limitation, SharePoint provides the “_spBodyOnLoadFunctionNames” array. When the body is loaded, the onload event handler executes each function whose name is contained in this array.
So apparently all one has to do to have a JavaScript function execute when the body loads is to add the name of the function (as a string) to that array, a la _spBodyOnLoadFunctionNames.push("functionName"); – simples!
D’oh!
In the end we just wanted to do to much for simple JavaScript so used the awesome jQuery library – which includes the $(document).ready() method to take care of that, but I’m sure the above will help somebody, somewhere, some day.