Are inner function declarations safe?

Question

function outer(x) {
    function inner(y) {
        if (y) console.log(y);
        else console.log(42);
    }
    inner(x + 1);
}
outer(5); // expect a logging of '6'
inner(); // expect a Reference Error

I know what it is supposed to do and I expect it to do just that but are there any cross-browser quirks or side effects I should be aware of when declaring inner functions.

[Edit]

By safe I meant is it possible they pollute global namespaces or are not treated as being local to the function they were declared in.

[/Edit]

Felix Kling · Accepted Answer · 2011-01-24T10:19:59.257

1

Afaik no. IE has problems with named function expressions like:

var inner = function inner2() {

}

but everything else should be fine.

edited Jan 24 '11 at 10:19

answered Jan 24 '11 at 10:11

Felix Kling

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Does that named function expression when used as an inner function hoist the scope of the funcion `inner` to global namespace? – Raynos Jan 24 '11 at 10:15
@Raynos: No, IE just creates two functions instead of one, but they stay in the same scope. – Felix Kling Jan 24 '11 at 10:20
Are there any strange side effects of using `var name = function name() { ... }` Where your using the same name for the function declaration & function expression in IE? – Raynos Jan 24 '11 at 10:27
@Raynos: Not 100% sure. The worse thing is that IE would still create two functions but one name would shadow the other one. – Felix Kling Jan 24 '11 at 10:49

score 0 · Answer 2 · edited May 23 '17 at 12:11

That's regular ECMAScript syntax. It allows for closures and "inner functions". Statements (function declarations and var) within a function are scoped within that function.

In your example, the function inner exists only within outer's scope; anything else than a Reference Error when trying to call inner() should be considered a "quirk".

UPDATE: Found a question probably related to this one.

score 0 · Answer 3 · answered Jan 24 '11 at 10:14

0

I'm not sure what you mean by "safe". In your example there is no way to invoke inner() from outside of outer(). If "safe" - means only function visibility, then your are right, it's safe.

answered Jan 24 '11 at 10:14

Alexandr

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By safe I meant is it possible they pollute global namespaces or are not treated as being local to the function they were declared in. – Raynos Jan 24 '11 at 10:19
inner - is treated as being local to the outer – Alexandr Jan 24 '11 at 10:39

Are inner function declarations safe?

3 Answers3