Safari/Chrome:  SyntaxError: Unexpected token '>'
  Firefox: SyntaxError: syntax error

In a discussion about Javascript maybe it would be a good idea to give examples of Javascipt that actually run in a Javascript console?

Firefox Nightly

    [1,10,5,-15,-2,4].sort ((a, b) => a-b).toString();
    "-15,-2,1,4,5,10"

You have responded to my pointing out that '->' syntax doesn't work in current browsers with an example of a different bit of syntax, '=>', that works in a single development browser. I don't follow your point.

Sorry you asked for an example which works in a Javascript console, I gave one, if you were trying to make a snarky reply about the state of es6 support in modern browsers then I misread it.

Actually when I posted it I was honestly unaware if that was ES6 Javascript or just Coffescript or something. People seem to throw them all about interchangeably which is very confusing to people like me who don't follow Javascript development.

People dont write JS just for Firefox Nightly.

I didnt say they should (some people do), it is code which works with a JavaScript console though