Javascript Conflicting Syntax Between Function As Object Key And Labeled Function In Block

Assuming you have a browser that supports both labeled function declarations and block statements, what is the standard way/method for browsers to determine if the following is an

Solution 1:

You can reduce the question to: How does the browser know whether { starts a block and when does it start an object literal?

And the answer to that is that JS engines will treat { as the start of a block if it appears in a statement position and as the start of an object literal if it is in an expression position.

That's the reason why you have to add parenthesis (()) around {} when they appear in a statement position but you want an object instead.

The introduction of labeled function declarations doesn't change the circumstances at all because the situation was already ambiguous:

{
  foo: 42
}

---

Looking at the spec again, this ambiguity is actually pointed out:

An ExpressionStatement cannot start with a U+007B (LEFT CURLY BRACKET) because that might make it ambiguous with a Block.

(and the grammar reflects that too)

Solution 2:

Well... I think that:

if(1){ // the brackets here belong to the if statement == block
    L: function F(){}
}

While here:

console.log({ // the brackets represent JSON (javascript object notation) L: functionF(){}
})

This is indeed an object with 'L' index