Multiple ways of extending javascript objects

/**
 * One-way reference from subclass to superclass (instance)
 * Most of the time this is what you want. It should be done
 * before adding other methods to Subclass.
 */
ChildClass.prototype = new SuperClass();
 
/**
 * Two-way reference
 * Superclass will also get any Subclass methods added later.
 */
ChildClass.prototype = SuperClass.prototype;
 
/**
 * Cloning behavior
 * This does not setup a reference, so instanceof will not work.
 */
angular.extend(ChildClass.prototype, SuperClass.prototype);
 
/**
 * Enhancing a single instance
 * This could be used to implement the decorator pattern.
 */
angular.extend(subClassInstance, SuperClass.prototype);