wikipedia says it was ES6 (6th Edition – ECMAScript 2015) Read the paragraph the link takes you to and you will see it mentions... "new collections (maps, sets and WeakMap)..."
However, W3Schools says it was first included in ES5 (2009).
The link displays numerous items include Array.Map().
Do you know when it was first added?
Very interesting because I thought it was first added to ES6, however, I found the official ES5 (2009) Spec PDF and found the following:
Of course, it is also defined in the ES6 Spec...
I had been under the impression it wasn't available until 2015, but it looks as if some browsers as far back as 2010 or so may have included it.