That’s not very JavaScript-y. Where else in ECMAScript are constants used like this?

That would be a Chromium feature. V8 only implements ECMAScript and WebAssembly.

The article is two years old but still up-to-date. The links to the relevant browser bugs are in the document, and the Edge bug is still unresolved. https://wpdev.uservoice.com/forums/257854-microsoft-edge-dev...

> Which means you can’t practically use the new form without feature detection.

That does not follow.

`{ capture: true }` works in both, since it’s an object, and thus truthy.

There’s no need for feature detection in the case you describe.

Sadly, that’s the whole premise of this article.

It’s only a problem if you want `capture: false` combined with other options — since you’d need to pass in an object, that would be truthy in the old implementations expecting a boolean instead. But then again, the additional options wouldn’t be supported in those old implementations either.

I’m confused — what’s the actual use case that’s breaking here?

In older browsers, useCapture is NOT an optional parameter, and in most cases you do NOT want to use event capture instead of event bubbling. There's no trivial way to support addEventListener(event, handler, { passive: true }) on both new and old browsers without that really ugly feature detection code in the article.

> In older browsers, useCapture is NOT an optional parameter

Which browsers are those?

That’s not equivalent though — in the article’s example, imagine `element` is `undefined`, for example. `then()` wouldn’t be called in that case.

Correct. By Stage 3, the proposal is supposed to be stable enough to start shipping it in stable browsers.

Wondering what a given legacy HTML color value (as seen in `bgcolor`, `text`, `link`, `vlink`, and `alink` attribute values) looks like? This tool (which I made for a presentation years ago) shows you: https://mothereff.in/bgcolor#mathiasbynens

Present tense: https://domenic.github.io/streams-demo/

Replace `test` with `example.com` et voila.

+1. Still, code screenshots in Notepad?!