A simple JavaScript class for DOM object property animation without jQuery. - http://jsfiddle.net/louisbros/bkVQX/

Animator.js

function Animator() {
    this._animated = [];
    this.EASING = {
        easeInOutCubic: function (e, f, a, h, g) {
            if ((f /= g / 2) < 1) {
                return h / 2 * f * f * f + a;
            }
            return h / 2 * ((f -= 2) * f * f + 2) + a;
        },
        easeOutBounce: function (e, f, a, h, g) {
            if ((f /= g) < (1 / 2.75)) {
                return h * (7.5625 * f * f) + a;
            } else {
                if (f < (2 / 2.75)) {
                    return h * (7.5625 * (f -= (1.5 / 2.75)) * f + 0.75) + a;
                } else {
                    if (f < (2.5 / 2.75)) {
                        return h * (7.5625 * (f -= (2.25 / 2.75)) * f + 0.9375) + a;
                    } else {
                        return h * (7.5625 * (f -= (2.625 / 2.75)) * f + 0.984375) + a;
                    }
                }
            }
        }
    };
}
Animator.prototype = {

    constructor: Animator,
    animate: function (object, property, unit, from, to, duration, easing, callBack, iterationCallBack) {

        var self = this;

    	if(from === to){
			return;
		}

        for (var i = 0; i < this._animated.length; i++) {
            if (this._animated[i].object === object && this._animated[i].property === property) {
                return;
            }
        }

        this._animated.push({
			'object': object,
            'property': property
        });

        object[property] = from + unit;
        var start = new Date().getTime();
        (function _animate() {
            var now = new Date().getTime() - start;
            var ease = self.EASING[easing](0, now, 0, 1, duration);
            object[property] = (from + (to - from) * ease) + unit;
            if (now < duration) {
                if (iterationCallBack) {
                    iterationCallBack();
                }
                setTimeout(_animate, 1000 / 60);
            } else {
                object[property] = to + unit;
                for (var i = 0; i < self._animated.length; i++) {
                    if (self._animated[i].object === object && self._animated[i].property === property) {
                        self._animated.splice(i, 1);
                        break;
                    }
                }
                if (callBack) {
                    callBack();
                }
            }
        })();
    }
};