Discussion on: PHP 8 features I wish also existed in JavaScript

[Bob]

The way you'd used named parameters in JavaScript OR TypeScript is through the use of an object:

JavaScript:

function test ({ a, b, c, d }) {
    ...
}

test({ a: 'test', b: 'test', d: 'test' });

TypeScript:

interface testing {
    a: string;
    b: string;
    c?: string;
    d?: string;
}

function test ({ a, b, c, d }: testing) {
    ...
}

test({ a: 'test', b: 'test', d: 'test' });

The way you'd use optional chaining is actually available in ESNext now:

const country =
  session?.user?.getAddress?.()['country']
  ? session.user.getAddress()['country']
  : null;

[Andreas]

Thank you for giving these examples! As I wrote in the article, I know about using object destructuring for named arguments, but I don't like this approach very much here - just doesn't feels like clean coding style to use an object inside the functions parameter definition. I can't think of a reason, why JavaScript doesn't already provide "real" named arguments already...

optional chaining is actually available in ESNext now

Great, didn't know that! 👏🏻

[Bob]

I agree 100%, however, it would drastically hinder performance as it would almost guaranteed be a runtime check in the engine. That's why I'm hoping either Babel or TypeScript will tackle it in the future to essentially be compiled away into positional arguments.

[Valeria]

Not sure I follow your thought. Typescript performs type checks on compilation only and strips all the types away, so there's never a runtime check.
Update: Oh you mean for chaining arguments? There's zero to none performance loss

[Bob]

We're discussing named parameters and the performance hit they would be on JavaScript's runtime.

And TypeScript does a whole lot more than type checking nowadays.

[Conan]

I must chime-in with a report from experience.

Some years ago I worked on a fairly large (~700k lines) JavaScript codebase that implemented a 200-line helper that permitted the following:

function get () {
  var opts = defaults(arguments, {
    byId: null,
    theseItems: '*',
  });
  return [opts.byId, opts.theseItems];
}

get();             // [null, '*']
get(2, 'cats');    // [2, 'cats']
get({ byId: 1 });  // [1, '*']

It was used extensively, including in time-critical places such as during render operations. While there was a performance hit that could be measured with dev-tools, it was nothing compared to the usual day-to-day bottlenecks that were encountered.

The point is to say that sure, worry about performance, but perhaps rest/spread/destructuring isn't the first place you need to look these days.