Safari 9 requires polyfill?

[Maxim-Filimonov]

Just noticed that the following warning pops up in Safari 9:
[Warning] webpack-hot-middleware's client requires EventSource to work. You should include a polyfill if you want to support this browser: https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events#Tools

According to w3c spec eventsource interface need to have a constructor but it doesn't necessary need to be a function.
It is an object in Safari 9 with following properties

EventSourceConstructor = $1
CLOSED: 2
CONNECTING: 0
OPEN: 1
length: 1
prototype: EventSourcePrototype {URL: undefined, url: undefined, withCredentials: undefined, readyState: undefined, …}
Object Prototype

Is there any reason why not to just check for window.EventSource !== undefined instead of requiring EventSource to be function?

[glenjamin]

Welp, I learned something new today - the spec says it has to be newable, and apparently Safari makes this work on objects.

I'll accept a PR that makes the check more naive in order to cover this case.

[glenjamin]

Will be released in 2.4.0

[Maxim-Filimonov]

@glenjamin Great, thanks! Btw you can probably simplify it even further to window.EventSource === undefined instead of doing typeof

[glenjamin]

Probably, but for some reason I always feel safer with typeof :)