Animate things without jQuery

Animator.js

// Original code from http://gabrieleromanato.name/javascript-implementing-the-fadein-and-fadeout-methods-without-jquery/
// Modified by Sony? aka Sawny
var Animator = {

    // Uses "jQuery" style / standard style. So you can easly import easings from jQuery
    // or other resources
    //
    // Format:
    // percent | elapsed time | start value | end value | total duration
    // x       | t            | b           | c         | d
    easing: {
        linear: function(x, t, b, c, d) {
            return b+c*x;
        },

        easeOutExpo: function (x, t, b, c, d) {
            return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
        }
    },

    animate: function(options) {
        var start = new Date;

        options.complete = options.complete || function() {};

        var id = setInterval(function() {
            var timePassed = new Date - start
            ,	progress   = timePassed / options.duration;

            if (progress > 1) {
                progress = 1;
            }

            if(options.from > options.to) {
                var delta = Animator.easing[options.easing](progress, timePassed, options.to, options.from, options.duration);
                    delta = options.from - delta;
            }
            else {
                var delta = Animator.easing[options.easing](progress, timePassed, options.from, options.to, options.duration);
            }

            options.step(delta, options.element);

            if (progress == 1) {
                clearInterval(id);
                delete options.element.quoAnimationID;
                options.complete();
            }
        }, options.delay || 10);

        options.element.quoAnimationID = id;
    }
};



//--------------------------------
// Example implemenation:
// 
// this = querySelector();


$$.fn.fadeIn = function(duration, easing, cb) {
    Animator.animate({
        duration: duration,
        element: this,
        complete: cb,
        easing: easing,
        to: 1,
        from: 0, 

        step: function(delta, element) {
            element.css('opacity', delta);
        }
    });
};


$$.fn.fadeOut = function(duration, easing, cb) {
    Animator.animate({
        duration: duration,
        element: this,
        complete: cb,
        easing: easing,
        to: 0,
        from: 1

        step: function(delta, element) {
            element.css('opacity', delta);
        }
    });
};


$$.fn.stopAnimation = function() {
    clearInterval(this.quoAnimationID);
    delete this.quoAnimationID;
};