If I understood it correctly you are looking to see which all libraries( or packages) are there in the final build. In case you are using webpack try webpack-bundle-analyzer. In case you are using browserify Disc can help you.

Singletons are the one's that can be initialized only once. In the simplest possible terms here is a singleton for you. var singleton = { key: "value" }; Another way var Singleton = (function(){ var instance; var SingletonClass = function(){ this.someProp = "someValue"; // all other stuff you want on your singleton instance; }; return { getInstance: function(){ if(!instance){ instance = new SingletonClass(); } return instance; } } })(); var aSingleton = Singleton.getInstance(); var bSingleton = Singleton.getInstance(); console.log(aSingleton.someProp); //someValue console.log(bSingleton.someProp); //someValue aSingleton.someProp = "someOtherValue"; console.log(a.someProp); //someOtherValue console.log(b.someProp); //someOtherValue In case you want to use new keyword for initialization var Singleton = (function () { var instance; function SingletonClass() { this.someProp = "someValue"; // all other stuff you want on your singleton instance; if (instance) { return instance; } instance = this; } return SingletonClass; }()); var aSingleton = new Singleton(); var bSingleton = new Singleton(); console.log(aSingleton.someProp); //someValue console.log(bSingleton.someProp); //someValue aSingleton.someProp = "someOtherValue"; console.log(aSingleton.someProp); //someOtherValue console.log(bSingleton.someProp); //someOtherValue Hope it helps.