What does javascript function return in the absence of a return statement?

Question

I was just wondering, does a function without a return statement (or without hitting any return statements) return a value that is completely equivalent to false? For example: ``` function foo(){}; !!foo(); ``` This should return false if executed in firebug (but does not return anything if i just called foo();). Thanks a lot! Jason

Accepted Answer

A function without a return statement (or one that ends its execution without hitting one) will return `undefined`.

And if you use the unary negation operator twice on an `undefined` value, you will get `false`.

You are not seeing anything on the console because Firebug doesn't prints the result of an expression when it's undefined (just try typing `undefined;` at the console, and you will see nothing).

However if you call the `console.log` function directly, and you will be able to see it:

```
function foo(){}

console.log(foo()); // will show 'undefined'
```

What does javascript function return in the absence of a return statement?

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