It looks like JQuery does the search in the current document when using a selector.
JQuery
document
How to search for an element only inside a div
div
var elems = jQuery(".foo", jQuery("#divYourWantToLimitTo") ); //BAD //or var elems = jQuery("#divYourWantToLimitTo .foo"); //Better //or var elems = jQuery("#divYourWantToLimitTo").find(".foo"); //BEST