Turn your JavaScript constructor functions into Singletons.

Singletonizer.js

//  deploytonenyures.blogspot.com

var singletonizer = {
	singletonize: function(initialFunc){
		if (typeof initialFunc != "function") 
            throw new TypeError("singletonizer.singletonize called on a non function");
		
		//desingletonize works also as a flag to know if the function has been singletonized		
		if (initialFunc.desingletonize)
			return initialFunc;		

		var instance;		
		function core(){
			if (!instance){
				//using aux to follow the "new" operator behaviour in case the constructor function returns a value
				//we're passing arguments around, but indeed it does not make much sense to singletonize a function expecting parameters
				var aux = initialFunc.apply(this, arguments); 
				instance = aux || this;
			}
			return instance;
		};

		//we're using the eval trick so that our singletonized function can keep the name of the original function, otherwise it would be empty	
		//eval runs in the current scope, so it traps "core" and "this" in the closure
		eval ("var singletonizedFunc = function " + initialFunc.name + "(){"
			+ "core.apply(this, arguments);"
			+ "return this;"
		+ "};");
		
		singletonizedFunc.desingletonize = function(){
			return initialFunc;
		};
		singletonizedFunc.prototype = initialFunc.prototype;
		return singletonizedFunc;
	},
	
	desingletonize: function(func){
		if (typeof func != "function") 
            throw new TypeError("singletonizer.desingletonize called on a non function");
		
		return func.desingletonize ? func.desingletonize() : func;
	}		
};


if (typeof module !== "undefined" && module.exports){
	exports.singletonizer = singletonizer;
}

Singletonizer.test.js

if (typeof module !== "undefined"){
  var singletonizer = require("./Singletonizer").singletonizer;	
}

function NetworkManager(server){
  console.log("NetworkManager constructor " + server);	
	this.creationTime = Date.now();
	this.server = server;
}

var nm1 = new NetworkManager("server1");

console.log("- singletonize:");
singletonizedNM = singletonizer.singletonize(NetworkManager);
var nm2 = singletonizedNM("server2");
var nm3 = singletonizedNM("server3");

console.log ("nm2.creationTime == nm3.creationTime" + (nm2.creationTime == nm3.creationTime));
console.log("singletonizedNM.name: " + singletonizedNM.name);

console.log("- desingletonize:");
var desingletonizedNM = singletonizedNM.desingletonize();
var nm4 = desingletonizedNM("server4");
var nm5 = desingletonizedNM("server5");