A must have function argument~ Implementations ~

A must have function argument

As we know, JavaScript is not a strictly typed language. We don't have types by default. That is why a big part of the community started using alternatives (like TypeScript). Which is a good solution, but most of them work at build time. Once our code is transpiled and bundled, the type checks are gone. Some time ago, I found a neat way to make a function argument required, even at runtime.

function required() {
  throw new Error(`Missing argument.`);
function shoppingCenter(time, money = required()) {
  return {

console.log(shoppingCenter("1h", 200));
// { time: '1h', money: 200 }

// Error: Missing argument.

This may be a bit drastic because throwing an error may lead to an application crash. However, with a proper error handling is a good solution.