JavaScript API that loads and houses libraries of code

Question

I have written a JavaScript API that loads and houses libraries of code to do all sorts of things on websites.

Effectively, this is (will be) the base JavaScript for all the websites I build.

The aim of this API is to load the required libraries (SM.load()) needed for a particular page, and add them to the library as a plugin (SM.run()).

You may be surprised as to how I have written this library, just to explain in brief. I have aliased the jQuery selector, so that if you run:

SM('#test').foo()

It will retrieve #test using the jQuery constructor function and then chain the result through to the foo() function. However, you can also run functions like this:

SM.bar()

Effectively this just mimics the way you can do this in jQuery:

$('#test').show()
$.ajax(options)

---

/**
 * Sine Macula Javascript API
 * The Sine Macula API contains all base functions for the Sine Macula
 * Javascript Library
 * @name class.sinemacula.js
 * @author Ben Carey
 * @version 1.0
 * @date 20/11/2012
 * @copyright (c) 2012 Sine Macula Limited (sinemaculammviii.com)
 */
(function(global, $){
 // Enable strict mode
 "use strict";
 // Set the global variables for Sine Macula
 var oldSM, SM;
 // Make sure jQuery has loaded
 if(typeof $ !== "function"){
 throw "jQuery must be loaded";
 }
 /**
 * Sine Macula Object
 * The main Sine Macula library
 *
 * @param string The element to be selected
 */
 SM = global.SM = global.SineMacula = SineMacula;
 function SineMacula(selector){
 // Construct and return an instance of the
 // Sine Macula object
 return new _initialize(selector);
 }
 /**
 * Sine Macula Constructor
 * Alias of the jQuery Selector
 *
 * @param string The element to be selected
 */
 function _initialize(selector){
 // Retrieve the elements matching the selector
 // and make it available to all the Sine Macula
 // methods
 this.elements = $(selector);
 }
 // So that plugins can add to _initialize.prototype, make it available
 // as a property of SineMacula: SineMacula.fn (aka SM.fn)
 SM.fn = _initialize.prototype;
 /**
 * Sine Macula Run
 * Makes it easy to write plugins for the Sine Macula library
 *
 * @param function callback
 */
 SM.run = run;
 function run(callback){
 // Call the function with the Sine Macula
 // and jQuery objects
 callback(SM, $);
 }
 /**
 * Sine Macula Load
 * Load the Sine Macula Libraries and Plugins
 * into the current document
 *
 * The options:
 * - package: the package of libraries to load
 * - packageURL: a remote source to load the package details from
 * - libraries: any additional libraries to load
 *
 * @param object options The options for the Sine Macula load
 */
 SM.load = load;
 function load(options){ 
 var url,query,script; 
 // Set the defaults for the loader
 var options = $.extend({
 package: 'none', // Do not load any packages by default
 packageURL: false, // Do not retrieve the package details from a URL by default
 libraries: [] // Do not load any libraries by default
 },options); 
 // Build the query based on the parameters supplied
 if(options.packageURL){ 
 // Build the query to allow for a remote
 // package definition
 query = '?packageURL='+encodeURIComponent(options.packageURL);
 }else if(options.package=='none'){ 
 // If no package has been supplied then just
 // provide libraries to load
 query = '?libraries='+encodeURIComponent(options.libraries.join());
 }else{ 
 // If a package has been supplied then
 // request it, and any additional libraries
 query = encodeURIComponent(options.package)+'/?libraries='+encodeURIComponent(options.libraries.join());
 } 
 // Complete the url by appending the query
 url = '//libraries.sinemaculammviii.com/'+query; 
 // Append the script tag to the end of the document
 script = document.createElement('script');
 script.type = 'text/javascript';
 script.src = url;
 $('head')[0].appendChild(script); 
 }
 /**
 * IndexOf
 * A fix to allow the call of the indexOf function
 * in Internet Explorer
 */
 if(!Array.prototype.indexOf){
 Array.prototype.indexOf = function (searchElement /*, fromIndex */ ) {
 "use strict";
 if (this == null) {
 throw new TypeError();
 }
 var t = Object(this);
 var len = t.length >>> 0;
 if (len === 0) {
 return -1;
 }
 var n = 0;
 if (arguments.length > 1) {
 n = Number(arguments[1]);
 if (n != n) { // shortcut for verifying if it's NaN
 n = 0;
 } else if (n != 0 && n != Infinity && n != -Infinity) {
 n = (n > 0 || -1) * Math.floor(Math.abs(n));
 }
 }
 if (n >= len) {
 return -1;
 }
 var k = n >= 0 ? n : Math.max(len - Math.abs(n), 0);
 for (; k < len; k++) {
 if (k in t && t[k] === searchElement) {
 return k;
 }
 }
 return -1;
 }
 }
})(this, this.jQuery);

• Florian Margaine: SM? Really?
• rlemon: related
• Ben Carey: @FlorianMargaine Hahahaha, oh dear!! Didnt think of that!! It stands for Sine Macula. I may change that now!
• Florian Margaine: @BenCarey And btw fix your indexOf shim. Right now, it shims all the time even when the method exists. See the official shim.
• Ben Carey: @FlorianMargaine Thank you very much, have amended my script :-)

Answer 1

From a once over:

• I like use strict in an IIFE
• However, the second use strict in indexOf is overkill
• You are not using the variable oldSM
• Lots of comments are good as well

• The below code is prepending really, and the hostname should be called out in separate variable or even better be derived from window.location

  // Complete the url by appending the query
  url = '//libraries.sinemaculammviii.com/'+query; 
  

• From a design perspective, I am not sure what you are providing with your script, except for a shell over jQuery. jQuery even has jQuery.getScript() which could replace
  

  // Append the script tag to the end of the document
  script = document.createElement('script');
  script.type = 'text/javascript';
  script.src = url;
  $('head')[0].appendChild(script); 
  

  it also has jQuery.inArray which you could use instead of your indexOf shim.