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I've seen that in some projects, Module Pattern uses instead of Singleton Pattern and vice versa.
I want to know exactly, what's the different between Module Pattern and Singleton Pattern?
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In javascript we can use module as singleton.
Modules are “singletons” in Python because import only creates a single copy of each module; subsequent imports of the same name keep returning the same module object.
For Dependency Injection, typically you would create an instance of the service outside of the target object (the client) and pass it to the client. For a Singleton, the object instantiates itself only once and you can only get/set properties or use methods of the object; you cannot create a new singleton object.
A singleton pattern ensures that you always get back the same instance of whatever type you are retrieving, whereas the factory pattern generally gives you a different instance of each type. The purpose of the singleton is where you want all calls to go through the same instance.
Module pattern in javascript refers to the modularisation of code for a common mechanism. It works quite well to split one "class" across several files as you can define constructor and various groups of prototype methods independently. Each of the modules is usually wrapped inside a closure to create static, local variables - this is called revealing module pattern.
Singleton pattern in javascript refers to the restriction of instance creations, often using lazy initialisation.
Of course you can consider the module pattern to be a specialisation of the singleton pattern (see the Wikipedia article), the constructor and its prototype object would take the part of the "single instance" then.
Yet you also could combine them "independently": A module that defines a class which uses the singleton approach.
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