Frame animation object

FrameAnimation.js

////////////////////////////////////////////////////////////////////////////////
// Frame animation object
////////////////////////////////////////////////////////////////////////////////
;namespace.display.FrameAnimation = (function(win, doc, ns)
{
    "use strict";
    //--------------------------------------------------------------------------
    //  Import
    //--------------------------------------------------------------------------
    var AnimationEvent = ns.event.AnimationEvent,
        EventDispatcher = ns.event.EventDispatcher;

    //--------------------------------------------------------------------------
    //  Variables
    //--------------------------------------------------------------------------

    //--------------------------------------------------------------------------
    //  Public methods
    //--------------------------------------------------------------------------
    /**
     * Keep FPS animation object
     *
     * @param {Object|String} target HTML element or ID name.
     * @param {String} className     Draw class name.
     * @param {Number} targetTime    One time length
     * @param {Number} frameNumber   Total frame number
     * @param {Number} endFrame      Not to loop
     * @constructor
     */
    var FrameAnimation = function(target, className, targetTime, frameNumber, endFrame)
    {
        EventDispatcher.apply(this);

        var element = (typeof target === 'string') ? doc.getElementById(target) : target,
            start = 0,
            state = 0,
            frame = 0,
            currentFrame = 0,
            fnumber = frameNumber + 1,
            finishFrame = endFrame || false,
            dispatchEvent = this.dispatchEvent;

        /**
         * Current frame number
         *
         * @type {Number}
         */
        this.currentFrame = 0;

        /**
         * Draw
         *
         * @param {Number} now time
         */
        this.draw = function(now)
        {
            now = (now || Date.now());

            switch (state)
            {
                case 0:
                    state = 1;
                    start = Date.now();
                    dispatchEvent(AnimationEvent.START);
                    break;
                case 1:
                    frame = ~~((now - start) / targetTime * fnumber);
                    state = (finishFrame && frame >= finishFrame) ? 2 : 1 ;
                    currentFrame = this.currentFrame = frame % fnumber;
                    element.className = className + currentFrame;
                    dispatchEvent(AnimationEvent.UPADATE);
                    break;
                case 2:
                    state = 4;
                    dispatchEvent(AnimationEvent.END);
                    break;
            }
        }
    };

    //--------------------------------------------------------------------------
    //  Private methods
    //--------------------------------------------------------------------------

    //--------------------------------------------------------------------------
    //  Export
    //--------------------------------------------------------------------------
    return FrameAnimation;

})(window, document, window.namespace);