Javascript Syntax with [...] in front of a function call / constructor call

Question

I have found a syntax in javascript I have never seen before and I was unable to find the right documentation.

It comes from a tutorial:

var connection = new [webkit|moz]RTCPeerConnection(...)

I can find by myself what webkit means and what moz means, presumably these are two defined constants or enums.

but my question is:

What does the syntax [webkit|moz] mean in those squared brackets?

Is is some kind of typecasting the result of the function result?

And what does the | character mean in [webkit|moz] - is this the OR operator?

thx

Answer 1

That's not proper javascript syntax (if you try running it, you'll get an unexpected token error at the first [), It just means you have to use either in your code, ie.:

new mozRTCPeerConnection()

for Firefox, and

new webkitRTCPeerConnection()

for webkit based browsers.

See the MDN docs on RTCPeerConnection:

Because this technology's specification has not stabilized, check the compatibility table for the proper prefixes to use in various browsers.

and

Warning: RTCPeerConnection and RTCSessionDescription are currently prefixed in most browsers. You should include a polyfill if you're using it in any work.