A simple implementation of Interfaces in Javascript. Allows you to define Interfaces with a bunch of methods. Defines Function.prototype.implement to be called on constructor functions which want to implement an interface. Throws errors if not all interface methods were declared.

gistfile1.js

function Interface(methodNames) {
	var self = this;
	methodNames.forEach(function(name) {
		self[name] = function() {
			throw new Error('Interface methods should not be called directly. Overwrite with specific implementation details.');
		};
	});
}

Function.prototype.implement = function(_interface, methodHash) {
	var proto = this.prototype = {};
	for (var prop in methodHash) {
		if (typeof methodHash[prop] === 'function') {
			proto[prop] = methodHash[prop];
		}
	}
	for (var prop in _interface) {
		if (typeof _interface[prop] === 'function') {
			try {
				proto[prop]();
			} catch (e) {
				throw new Error('Did not declare Interface method named ' + prop + '. Go back and declare this method.');
			}
		}
	}
}

var UserRepo = new Interface(['get', 'save', 'edit', 'getAll']);

function UserRepoRedis() {
	// implementation-sepcific details
}
UserRepoRedis.implement(UserRepo, {
	get: function() {}
	, save: function() {}
	, edit: function() {}
	, getAll: function() {}
});