javascript - What is the difference between a closure and a module? - Stack Overflow

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I know that a module like this one:

function User(){
    var username, password;

    function doLogin(user, pw){
        username = user;
        password = pw;
    };
    var publicAPI = {
        login: doLogin
    };
    return publicAPI;
}

has a closure inside of it: doLogin, and is remembering the values of the variables username and password that are inside User, what makes this a "closure". What I don't quite understand is if whenever we use a closure we are using the module pattern? or as soon as I save the function of the User in a variable like var User = function(){... is not a module... Please bear in mind I'm learning js.

I know that a module like this one:

function User(){
    var username, password;

    function doLogin(user, pw){
        username = user;
        password = pw;
    };
    var publicAPI = {
        login: doLogin
    };
    return publicAPI;
}

has a closure inside of it: doLogin, and is remembering the values of the variables username and password that are inside User, what makes this a "closure". What I don't quite understand is if whenever we use a closure we are using the module pattern? or as soon as I save the function of the User in a variable like var User = function(){... is not a module... Please bear in mind I'm learning js.

• javascript
• function

Share Improve this question Follow asked Nov 20, 2015 at 11:39 Camilo SanchezCamilo Sanchez 1,28222 gold badges1313 silver badges1717 bronze badges 1

• 2 The module pattern is using closures, not the other way round. Closures are an integral part of the language, modules are just a pattern that emerged from them (and there's a lot of other things you can do with closures). – Bergi Commented Nov 20, 2015 at 12:31

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2 Answers 2

Sorted by: Reset to default 6

You have implemented a factory function for Users.

You are "almost" using the revealing module pattern. Most people would say the revealing module pattern would need to be invoked immediately. Module patterns are usually used for code organisation. What you have here instead is an object factory.

Closures are used by the (revealing) module pattern (and others) to achieve the encapsulation of private state.

A closure is created whenever a function is defined. They are a language feature of JavaScript to make working with functions easier.

Closures are a way to close over(or capture) information or state from the enclosing scope. Basically it is a means of extending the lifetime of a variable.

Modules are a way to hide the implementation and state from outside world.

So, doLogin() is closing over both username and password and thus increasing their lifetime. And object refereed to by publicAPI is hiding the implementation of doLogin() from the user

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