[esrauch]

> In JavaScript, {} + [] evaluates to integer 0.

This not really true. Put this js console and you'll see that a is the string "[object Object]":

  a = {}+[]

When you put just {}+[] in your console its doing an empty block followed by unary-plus,like:

  {/*do nothing block*/}; +[]

[jakear]

Huh that’s quite interesting. It behaves this way even when you explicitly make it an object literal rather than a block.

I guess JS’s parser explicitly prohibits adding things to a curly-brace enclosed entity?

I’m normally quite defensive of JS, but I’ll have to admit I don’t like that.

[Zarel]

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;
    }

[jakear]

Yes, I realized after the fact that I was indeed making a label. I’m now back to not having an issue with JS

[esrauch]

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.

[Non24Throw]

You’re right! I would never have guessed that. Learn something new every day.