on_resize.js

/* resize_function executes a function whenever the screensize changes.
   by Jamieson Becker. Public Domain (do what you will)
   requires jQuery or compatible.
 */

on_resize = function(f) {
    var still_running = false;
    var previous_height = 0;
    var previous_width = 0;
    if (!f) console.error("Please provide resize_function with a function");
    $(window).resize(function() {
        if (still_running) return;
        still_running = true;
        var height = $(window).height(); // New height
        var width = $(window).width(); // New width
        if (height != previous_height || width != previous_width) {
            setTimeout(function() {
                // get latest height and width at end
                var height = $(window).height(); // New height
                var width = $(window).width(); // New width
                f(previous_height, previous_width, height, width);
                previous_height = height;
                previous_width = width;
                still_running = false;
            }, 125);
        }
    });
}   

/* Example of usage. Pass in the function to get executed */

on_resize(
    function(ph, pw, h, w) { console.log ("Screen size has changed. New size: " + h + ", " + w); }
);

The whole point of this is that it protects against the resizing process - calling multiple times when it's actually only a single continuous event.