javascript - ES6 variable import by reference or copy

Question

Suppose i have a var.js

export let x = 1;
export const f = () => x = 5;

Then i execute this in another file

import { x, f } from './var.js';
console.log(x); // 1
f();
console.log(x); // 5

Why is the imported variable x able to change accordingly?

Does import { x } gets re-evaluated when x in var.js changes?

Or is x a reference to the original x in var.js rather than a copy?

Answer 1

ES6 import/exports are actually bindings (references). As the value of x in original file var.js changes, it's reflected in another file too.

Reference: http://2ality.com/2015/07/es6-module-exports.html