Do inner functions in JavaScript get hoisted? How do the scoping rules apply to them?

Question

I thought that JavaScript doesn\'t have block scope, but function scope, and that declarations are hoisted from their block to the top of their parent functions.

How

Answer 1

The declaration of inner is hoisted to the top of the outer function. However, its value is only set if a == 1.

When outer() is called with a different value, the call to inner(456) fails as inner is still set to undefined.

Answer 2

if (…) {
    function …() {            
        …
    }
}

is invalid ECMAScript. Function declarations must be on the top level of function or program bodies, inside of blocks their behaviour is implementation-dependent. Firefox does execute this function statement conditionally, other browsers do hoist it like a normal function declaration. Move it outside the if-statement, or assign a function expression.