player/js/utils/asset_loader.js

var assetLoader = (function(){

    function formatResponse(xhr) {
        if(xhr.response && typeof xhr.response === 'object') {
            return xhr.response;
        } else if(xhr.response && typeof xhr.response === 'string') {
            return JSON.parse(xhr.response);
        } else if(xhr.responseText) {
            return JSON.parse(xhr.responseText);
        }
    }

    function loadAsset(path, callback, errorCallback) {
        var response;
        var xhr = new XMLHttpRequest();
        xhr.open('GET', path, true);
        // set responseType after calling open or IE will break.
        try {
            // This crashes on Android WebView prior to KitKat
            xhr.responseType = 'json';
        } catch (err) {}
        xhr.send();
        xhr.onreadystatechange = function () {
            if (xhr.readyState == 4) {
                if(xhr.status == 200){
                    response = formatResponse(xhr);
                    callback(response);
                }else{
                    try{
                        response = formatResponse(xhr);
                        callback(response);
                    }catch(err){
                        if(errorCallback) {
                            errorCallback(err);
                        }
                    }
                }
            }
        };
    }
    return {
        load: loadAsset
    }
}())