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Generates a MooTools class that lazily loads the real class on first instantiation
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Generates a class that lazily fetches and loads the real class on first instantiation. Provides an extremely minimal and seamless API that should require no changes to existing code in most situations.

How To Use

Instantiate a new LazyClass by passing its constructor the name of the class to generate.

var ClassName = new LazyClass('ClassName');

A nearly empty class will be generated and assigned to ClassName. This is called the "prepared" state. The real class has not been loaded yet, but ClassName may be used just as if it has. On the first attempt to instantiate a ClassName instance, the class will be fetched with an XmlHttpRequest. ClassName will be redifined and replaced with the real ClassName, and the initial request for an instance of ClassName will return an instance of the real ClassName.

new ClassName('abc',123);


On-demand load. If the class has been prepared already but not instantiated and the user decides they need the class to be loaded now, load() will pull the source of the prepared class and replace the reference to it with the real one. This is most useful for accessing class methods, which will not exist in the prepared class, nor load the class when an attempt is made to call them (unless explicitly defined in the options).

ClassName = ClassName.load();
// or just


A utility class method that creates prepared classes for each of the passed Strings and defines them in the given scope (or window by default).

new ClassName0('some','args'); //causes class to be loaded

Arguments can also be given as an array. An options object may be provided as the final parameter regardless.

var classes = ['ClassName0','ClassName1','ClassName2'];
var options = {
    path: '/js/{class}.class.js',


All options passed to LazyClass.prepare are passed straight through to the LazyClass constructor for each class given to it. This is useful for using the same options to prepare many classes.

path (default: "./{class}.js")

A relative or absolute path to the source of the class to prepare. {class} will be replaced with the String that was provided as the class name. If the class was stored in the "js" folder in the root directory of the web server and was of the extension ".class.js", use the path option as show below.

var ClassName = LazyClass('ClassName',{path:'/js/{class}.class.js'});

scope (default: window)

The scope into which the class will be assigned and from which it will be accessed.

window.personalScope = {}
var classes = ['ClassName0','ClassName1','ClassName2'];
new personalScope.className2(0,1,2,3,4,5,6,7,8,9,'abc','def');

classMethods (default: [])

Allows the class to be lazily loaded on a call of any of the given class methods. In the following example, classMethod will invoke the loading process and then return the return value of the real class method.

new LazyClass('ClassName',{classMethods:'classMethod'});


  • Research better blocking solutions like getify's LABjs
  • Research promises and possibly perform a complete rewrite, promising that classes will exist by the time they are used

Known Issues

Due to the same-origin policy on the XmlHttpRequest object, classes need to be served from the same domain as the page running the javascript. Manipulation of document.domain can allow classes to be loaded from different domains that share a second-level domain for now. This should be good enough for most problems. There are some workarounds for this (most of which are gigantic hacks), and a proper solution is planned. Suggestions or contributions are welcome.

A method to synchronously request, download, and execute javascript from a remote host (preferably without same-origin restrictions) is being researched. Unfortunately, a simple solution like Utilities.Assets.javascript or Request.JSONP will not work, as they do not block. See links in the TODO section.

Additional Info

I am always open for feature requests or any feedback. I can be reached at Github.

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