Javascript file or module scope only variables

Question

Correct me if am wrong the function require() imports the .js file somehow as copy past it in the current document so if the var name was both in two modules would the second override the first?
and how can i define file scope only variables

note that i want to define my variable outside any function in my .js file and not it be in the global scope

what are the solutions, does using the keyword var affects the variable scope, what define the scope other than function in javascript, can module object be useful for defining private variables in one file

module1.js

var name = 'i am module 1' 

foo = () => console.log(name)

module.exports = foo

module2.js

var name = 'i am module 2' 

foo = () => console.log(name)

module.exports = foo

main.js

const module1 = require('./module1')
const module2 = require('./module2')

module1() // "i am module 1" or "i am module 2"?
module2() // "i am module 2"

"i am module 1" or "i am module 2"? so, which is it? it will only output one of those, what has your extensive testing shown you? — Jaromanda X
– Jaromanda X, Commented Dec 8, 2017 at 4:06
am a bit confused i used var keyword and not used it am stick now for using it cause that worked, i want to understand what defines the variable scope other than functions and how can i divide my project into separate files without worrying about polluting each other scopes — Hassan
– Hassan, Commented Dec 8, 2017 at 4:11

Arun Redhu · Accepted Answer · 2017-12-08 04:13:50Z

1

In javascript when you load the .js file directly in the '.html' file then the variables declared outside of the function get registered on global scope. To prevent this kind of things people starts using IIFE functions and wrap the single file in the IIFE. But in modern Javascript you can use modules like we used in Nodejs and module loader to load those files. Now modern browser supports ECMAScript modules and you can directly use them.

Main benefits of using modules is that you don't have to use IIFE function to prevent the variable registered on global scope. Now Every variable declared in that file are private to that file only unless you export it.

For Example: module1.js

var name = 'my name';

function getName(){
    return name;
}

module.exports  = {
    getName
}

In the above example name is private to this file only you can't use it in another file unless you export it.

answered Dec 8, 2017 at 4:13

Arun Redhu

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2 Comments

Hassan Over a year ago

so require() respects the modules.exports then how can you define a global var in the module and still using require(), Do you have to exported to become in the global scope ?

Arun Redhu Over a year ago

In Nodejs we can add properties to globals and in browsers we can add properties to window object but it is not the best practice to pollute the global scope. If you want to use properties or functions from one file to the other then you should export from that file and import/require into the other in which you want to use.

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