How / Where does JavaScript determine the default locale?

Question

Today, September 11, 2017, the JavaScript toLocaleDateString()method outputs 9/11/2017to me. But I'm in the UK, so formatting is wrong in this case. MDN Web Docs tell me that this method returns a "formatted string in the locale by default."

So where / how does JavaScript detect my standard locale? Where is this set, or what does it depend on, and (how) can I change it?

Edited to add: I am using Firefox 55.0.3 for Windows 10, if that matters.

Answer 1

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Answer 2

locale . . :

  var date = new Date().toLocaleDateString("en-GB");