In a jQuery handler, return false is shorthand for calling both preventDefault() and stopPropagation(). Most code that uses it only wanted the first — stopping the link from navigating — and gets the second without noticing, because nothing on the page is watching for the event yet at the time it is written.
$('#filters a').click(function (event) {
event.preventDefault(); // the link does not navigate
applyFilter(this.hash); // handlers further up still run
});
$('#filters a').click(function () {
return false; // navigation stopped, and the event stops here
});The consequence shows up later and somewhere else: a delegated handler bound on a container never fires, so a dropdown stops closing or a click counter stops counting, and nothing in either file suggests they are related. It is also worth knowing that return false in a plain DOM handler assigned to onclick only prevents the default — the double meaning is jQuery’s, not the browser’s. Call preventDefault() unless you have decided you want propagation stopped too.