_spBodyOnLoadFunctionNames.push & ExecuteOrDelayUntilScriptLoaded undefined.

Hi Experts,

I started learning share point 2010.

I tried to execute some java script but I am getting undefined error .

//_spBodyOnLoadFunctionNames.push("pageOnLoad");
 ExecuteOrDelayUntilScriptLoaded(pageOnLoad,'sp.js');

I tried both functions but it is showing error.

Can you please tell how to execute it.

Thanks

AshisK