How did you explicitly make it into an object literal?

    ({}) + []
    -> "[object Object]"

will correctly make it "[object Object]"

Did you try to do this?

    {a: 1} + []
    -> 0

That's interpreted as the statement 1 labeled a, not as an object. This makes it obvious it's not an object:

    {a: 1, b: 2} + []
    -> Uncaught SyntaxError: Unexpected token ':'

JavaScript supports labels so you can continue/break multiple levels at once:

    {
      a: while (true)
        while (true)
          break a;
    }

It's just ASI (automatic semicolon insertion) and at the top-level {} declares a block not an object.

You can also do like ({} + []) and it will actually be "adding" them; the confusion solely comes from people typing into the JS console something that wouldn't make any sense to put into an actual script.