What happens to variables when are not used in a module?

Question

utils.js

const array = [1,2,3,4,5,6,7,8];

export default (props)=>{return <div>{array.map(()=>do something)}</div>}

index.js

import Comp from './utils.js';

I know that when you require a module, it remains in memory cache, so if you call it twice it, the module will not run and give you back the exported functions.

In this case we have a const variable. The exported function has a reference to variable and because the exported function remains in cache that means that the const variable remains also and is not GB. Is this right? If not what does actually happen?

Yes, you're right. The same variable remains for the entire time. — Emile Bergeron, Sep 23 '20 at 13:39
I mean, you could just test it on your end and figure it out. — Emile Bergeron, Sep 23 '20 at 14:18
You can even export the array directly and it'll be shared across the app as well. — Emile Bergeron, Sep 23 '20 at 14:19
@EmileBergeron How could you test if a variable is still in memory? I want an article to share with my colleagues — George Paouris, Sep 23 '20 at 14:19
When you write `(props) => ...` you created a closure, and all of the variables from that scope are available inside your function. Those variables will remain in memory until your function (and other references to the variables) are garbage collected. — Mulan, Sep 23 '20 at 14:34

score 1 · Answer 1 · answered Sep 23 '20 at 14:21

Yes - the const variable stays, because you never set it to NULL.

This is because the closure-variables are still used when you keep a reference to them in the exported default that is cached. So the GC can never collect this variable/const (assuming the GC is not buggy).

What happens to variables when are not used in a module?

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