How can I include a JavaScript file in another JavaScript file?

ncrmxrg.js

// EXPORTING A DEFAULT
// separateFile.js
export default function foo() {
  console.log("bar");
}

// index.js

import foo from "./separateFile"

foo(); //--> "bar" 


/~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

//EXPORTING WITHOUT SETTING A DEFAULT
//seperateFile.js
export function foo() {
  console.log("bar");
}

// index.js

import {foo} from "./separateFile"

foo(); //--> "bar"