[jquery] Find an element by class name, from a known parent element

You were close. You can do:

var element = $("#parentDiv").find(".myClassNameOfInterest");

Alternatively, you can do:

var element = $(".myClassNameOfInterest", "#parentDiv");

...which sets the context of the jQuery object to the #parentDiv.

EDIT:

Additionally, it may be faster in some browsers if you do div.myClassNameOfInterest instead of just .myClassNameOfInterest.