Question

Select elements that i have previously set with jquery.data();

i.e. Select all elements with .data('myAttr') already been set.

SOLUTION

A jsfiddle to demostrate is Fiddle

Answer 1

You could do

$('[data-myAttr!=""]'); 

this selects all elements which have an attribute data-myAttr which is not equal to ” (so it must have been set); (only for elements that have their data attribute set in HTML not via jQuery)

you could also use filter() (which works for data attributes set from jQuery)

$('*').filter(function() {
    return $(this).data('myAttr') !== undefined;
});