jQuery get the location of an element relative to window

Question

Given an HTML DOM ID, how to get an element\'s position relative to the window in JavaScript/JQuery? This is not the same as relative to the document nor offset parent sinc

Answer 1

TL;DR

headroom_by_jQuery = $('#id').offset().top - $(window).scrollTop();

headroom_by_DOM = $('#id')[0].getBoundingClientRect().top;   // if no iframe

.getBoundingClientRect() appears to be universal. .offset() and .scrollTop() have been supported since jQuery 1.2. Thanks @user372551 and @prograhammer. To use DOM in an iframe see @ImranAnsari's solution.