simple require using jquery

kishalmi.js

/**
 * cheap require (using jquery)
 *  loads a script (or scripts, if given an array) and executes it
 *  callbacks for progress and success
 *  won't load a script twice if already loaded (or failed)
 * @param files
 * @param callbackProgress
 * @param callbackSuccess
 */
function require(files, callbackProgress, callbackSuccess) {
	// shift back if progress cb skipped
	if (!$.isFunction(callbackSuccess)) {
		callbackSuccess = callbackProgress;
		callbackProgress = null;
	}

	if (!$.required) // create jquery namespace for required files
		$.required = {
			_complete: 0,
			_pending: 0
		};

	var loadScript = function (file) {
		var req = $.required[file];
		if (!req) {
			req = $.required[file] = {
				status: 'pending',
				callbacks: []
			};
			// load script
			$.required._pending++;
			$.ajax({
				url: file,
				dataType: 'script',
				xhr: function () {
					var xhr = new window.XMLHttpRequest();
					xhr.addEventListener("progress", function (event) {
						if (event.lengthComputable && event.loaded < event.total && $.isFunction(callbackProgress))
							callbackProgress(($.required._complete + event.loaded / event.total) / $.required._pending);
					}, false);
					return xhr;
				},
				success: function (data) {
				},
				complete: function () {
					req.status = 'complete';
					$.required._complete++;
					if ($.isFunction(callbackProgress)) callbackProgress($.required._complete / $.required._pending);
					if ($.required._complete < $.required._pending) return;
					// call all success callbacks
					while (req.callbacks.length) {
						var cb = req.callbacks.shift();
						if ($.isFunction(cb)) cb();
					}
				},
				error: function (jqXHR, textStatus, errorThrown) {
					console.error('ERROR loading "' + file + '": ' + textStatus + ' (' + errorThrown.message + ')');
				}
			});
		}

		switch (req.status) {
			case 'pending':
				// add valid callbacks to queues
				if ($.isFunction(callbackSuccess))
					req.callbacks.push(callbackSuccess);
				break;
			case 'complete':
				// already done
				if ($.isFunction(callbackSuccess)) callbackSuccess();
				break;
				// already failed -> call error
				if ($.isFunction(callbackError)) callbackError(req.error);
				break;
		}
	};

	if (!$.isArray(files)) files = [files];
	$.each(files, function (key, value) {
		loadScript(value);
	});
}