A singleton class is one which can only ever have one instance. The concept is more useful in Java, where you cannot create an object without first creating a class. JavaScript allows objects without classes (indeed, it has no classes, only objects) but using Singleton lets you create custom objects from existing jsclass classes, allowing you to inherit methods, include modules and use method() et al.

// In the browser
JS.require('JS.Singleton', function(Singleton) { ... });

// In CommonJS
var Singleton = require('jsclass/src/core').Singleton;

To create a singleton:

var Camel = new Singleton(Animal, {
    fillHumpsWithWater: function() { ... }

// You can call instance methods...
Camel.speak('the desert');    // from Animal

var s = Camel.method('speak');

Camel.klass.superclass    // -> Animal

Singleton just creates a class with the arguments you give it, immediately instantiates this new class and returns the instance. You can access the class through Camel.klass as shown above.