jQueryMultiAjax.js

/*
 * Use to await multiple async ajax requests in a 'fire and forget' approach, with an even triggered 
 * on completion.  We used this to hold back the display of a lightbox until the outstanding requests
 * had fetched the data necessary for display - provided the user with a fully rendered lightbox, rather
 * than a skeleton within which multiple elements then shifted around or popped in.
 *
 * $(document).bind('data.retrieved',showMyLightbox);
 * multiGet('data.retrieved', {
 *         url:      '/redata/us-states/',
 *         success:  function(d) { populateSelectList('select#st',d); },
 *         error:    showAsyncErrorResponse},
 *     {
 *         url:      '/customer/address-info/',
 *         success:  populateAddressDiv,
 *         error:    showAsyncErrorResponse});
 */
Utils = {};

Util.argumentsToArray = function (args) {
    var idx, ary = [];
    for (idx = 0 ; idx < args.length; idx = idx + 1) {
        ary[idx] = args[idx];
    }
    return ary;
};

Utils.ajax = function (opts) {
    if ('POST' == opts.type || 'PUT' == opts.type) {
        if (!opts.data || opts.data.length == 0) {
            console.log('WARN: ajax request with no data: ' + opts.type + '; ' + opts.url);
        }
    }
    var origErrorHandler = opts.error;
    opts.error = function (request, textStatus, errorThrown) {
        if (origErrorHandler) {
            origErrorHandler.apply(this, arguments);
        }
    };
    $.ajax(opts);
};

Utils.get = function (opts) {
    Utils.ajax({
        url: opts.url,
        type: 'GET',
        dataType: opts.dataType || 'json',
        success: opts.success,
        error: opts.error
    });
};

Utils.multiGet = function () {
    var args, doneEvent, countdownLatch, decrementLatch, buildCallback;
    args = Utils.argumentsToArray(arguments);
    doneEvent = args.shift();
    countdownLatch = args.length;
    decrementLatch = function () {
        if ( 0 === --countdownLatch ) {
            $(document).trigger(doneEvent);
        }
    };
    buildCallback = function(eventName,callback) {
        return function (data) {
            if (eventName) {
                $(document).trigger(eventName);
            }
            callback(data);
            decrementLatch();
        };
    };
    jQuery.each(args,function (idx, params) {
        params.success = buildCallback(params.successEvent,params.success);
        params.error   = buildCallback(params.errorEvent,params.error);
        Utils.get(params);
    });
};