Source: d:/wamp/www/phaser/src/pixi/loaders/JsonLoader.js

/**
 * @author Mat Groves http://matgroves.com/ @Doormat23
 */

/**
 * The json file loader is used to load in JSON data and parse it
 * When loaded this class will dispatch a 'loaded' event
 * If loading fails this class will dispatch an 'error' event
 *
 * @class JsonLoader
 * @uses EventTarget
 * @constructor
 * @param url {String} The url of the JSON file
 * @param crossorigin {Boolean} Whether requests should be treated as crossorigin
 */
PIXI.JsonLoader = function (url, crossorigin) {

    /**
     * The url of the bitmap font data
     *
     * @property url
     * @type String
     */
    this.url = url;

    /**
     * Whether the requests should be treated as cross origin
     *
     * @property crossorigin
     * @type Boolean
     */
    this.crossorigin = crossorigin;

    /**
     * [read-only] The base url of the bitmap font data
     *
     * @property baseUrl
     * @type String
     * @readOnly
     */
    this.baseUrl = url.replace(/[^\/]*$/, '');

    /**
     * [read-only] Whether the data has loaded yet
     *
     * @property loaded
     * @type Boolean
     * @readOnly
     */
    this.loaded = false;

};

// constructor
PIXI.JsonLoader.prototype.constructor = PIXI.JsonLoader;

PIXI.EventTarget.mixin(PIXI.JsonLoader.prototype);

/**
 * Loads the JSON data
 *
 * @method load
 */
PIXI.JsonLoader.prototype.load = function () {

    if(window.XDomainRequest && this.crossorigin)
    {
        this.ajaxRequest = new window.XDomainRequest();

        // XDomainRequest has a few quirks. Occasionally it will abort requests
        // A way to avoid this is to make sure ALL callbacks are set even if not used
        // More info here: http://stackoverflow.com/questions/15786966/xdomainrequest-aborts-post-on-ie-9
        this.ajaxRequest.timeout = 3000;

        this.ajaxRequest.onerror = this.onError.bind(this);

        this.ajaxRequest.ontimeout = this.onError.bind(this);

        this.ajaxRequest.onprogress = function() {};

    }
    else if (window.XMLHttpRequest)
    {
        this.ajaxRequest = new window.XMLHttpRequest();
    }
    else
    {
        this.ajaxRequest = new window.ActiveXObject('Microsoft.XMLHTTP');
    }

    this.ajaxRequest.onload = this.onJSONLoaded.bind(this);

    this.ajaxRequest.open('GET',this.url,true);

    this.ajaxRequest.send();
};

/**
 * Invoked when the JSON file is loaded.
 *
 * @method onJSONLoaded
 * @private
 */
PIXI.JsonLoader.prototype.onJSONLoaded = function () {

    if(!this.ajaxRequest.responseText )
    {
        this.onError();
        return;
    }

    this.json = JSON.parse(this.ajaxRequest.responseText);

    if(this.json.frames)
    {
        // sprite sheet
        var textureUrl = this.baseUrl + this.json.meta.image;
        var image = new PIXI.ImageLoader(textureUrl, this.crossorigin);
        var frameData = this.json.frames;

        this.texture = image.texture.baseTexture;
        image.addEventListener('loaded', this.onLoaded.bind(this));

        for (var i in frameData)
        {
            var rect = frameData[i].frame;

            if (rect)
            {
                var textureSize = new PIXI.Rectangle(rect.x, rect.y, rect.w, rect.h);
                var crop = textureSize.clone();
                var trim = null;
                
                //  Check to see if the sprite is trimmed
                if (frameData[i].trimmed)
                {
                    var actualSize = frameData[i].sourceSize;
                    var realSize = frameData[i].spriteSourceSize;
                    trim = new PIXI.Rectangle(realSize.x, realSize.y, actualSize.w, actualSize.h);
                }
                PIXI.TextureCache[i] = new PIXI.Texture(this.texture, textureSize, crop, trim);
            }
        }

        image.load();

    }
    else if(this.json.bones)
    {
        // spine animation
        var spineJsonParser = new spine.SkeletonJson();
        var skeletonData = spineJsonParser.readSkeletonData(this.json);
        PIXI.AnimCache[this.url] = skeletonData;
        this.onLoaded();
    }
    else
    {
        this.onLoaded();
    }
};

/**
 * Invoked when the json file has loaded.
 *
 * @method onLoaded
 * @private
 */
PIXI.JsonLoader.prototype.onLoaded = function () {
    this.loaded = true;
    this.dispatchEvent({
        type: 'loaded',
        content: this
    });
};

/**
 * Invoked if an error occurs.
 *
 * @method onError
 * @private
 */
PIXI.JsonLoader.prototype.onError = function () {

    this.dispatchEvent({
        type: 'error',
        content: this
    });
};