Slimming Down JQuery Easing

January 2012 · 2 minute read

For simple javascript animations there is always a trade off between code size and visual effects. Recently I was trying to add some visual pizzazz to hour weather but didn’t want to incur the overhead of JQuery UI. What I was looking for was just a simple bounce effect on some moving objects. A lighter weight alternative that I considered was JQuery easing but even that seemed like overkill. My solution was to rip out the parts I needed and I wanted to share how easy that process is.

The Slim Down

After you grab the code for JQuery easing you’ll see that the plugin is a associative array with the animation type as the key and the animation function as the value. The functions are just a wrapper around the corresponding formula which handles the motion calculation.

To slim down the library it’s just a matter of removing each keyword/function pair that you aren’t planning on using.

You can take a look at my version which adds the bounce animation bellow or you can take a look at it in action at:

jQuery.easing['jswing'] = jQuery.easing['swing'];

jQuery.extend( jQuery.easing,
    def\: 'easeOutQuad',
    swing\: function (x, t, b, c, d) {
        return jQuery.easing[jQuery.easing.def](x, t, b, c, d);
    easeOutQuad\: function (x, t, b, c, d) {
        return -c *(t/=d)*(t-2) + b;
    easeOutBounce\: function (x, t, b, c, d) {
        if ((t/=d) < (1/2.75)) {
            return c*(7.5625*t*t) + b;
        } else if (t < (2/2.75)) {
            return c*(7.5625*(t-=(1.5/2.75))*t + .75) + b;
        } else if (t < (2.5/2.75)) {
            return c*(7.5625*(t-=(2.25/2.75))*t + .9375) + b;
        } else {
            return c*(7.5625*(t-=(2.625/2.75))*t + .984375) + b;