Ah yes, I had forgotten about Typed Arrays, which is a terrible name for what is in fact a buffer view. The entire arraybuffer/typedarray system was a later (≥IE10 if I am not mistaken?) hack added to make up for the fact that Array and Number are super inefficient for data processing.

But regardless of them being a bandaid, you are correct that it is an exception. ArrayBuffer and all its views count 10 types in total, so were they the only exception? If so, I believe my point still stands.

That's just how it optimizes their usage under-the-hood, but as far as JS is concerned they are all hash maps.

For example, try this:

    var foo = [1,2,3];  // or `foo = new Array(1,2,3)` also works
    foo['bar'] = 'test';
    console.log(foo);

and you get:

    0:1
    1:2
    2:3
    bar:"test"