Which part of the code executes inner function?

Asked Nov 21 '18 at 19:13

Active Nov 21 '18 at 19:31

Viewed 42 times

I came across this question in one of the online quizes. The solution I came up with was function. BUT, the console logs number.

var f = (
   function f(){return "1";},
   function g (){return 2;}
)();
console.log(typeof f);

My thinking was: var f becomes an IIFE, so typeof f should be a function.

Now, apparently, function g() inside var f executes and returns its value to var f, so the console logs number (or 2, if I just log f).

Questions:

1.What is the explanation for function comma anotherFunction. This is not an object, and also not a variable declaration (like var x, y;)?

2.Somehow the second function is the one that is being returned, but what part of the code is actually executing it?

(I thought that () just before the console.log call is executing the outer f function (which should just define inner functions f() and g(), but not execute any of them ). The second one gets executed, so , obviously, I was wrong.

asked Nov 21 '18 at 19:13

Yozex

you should remove the space after the `g` – andrea-f Nov 21 '18 at 19:15
1

There is no "outer function". – melpomene Nov 21 '18 at 19:15
1

Who in their right mind would even write such a thing... – Ben Steward Nov 21 '18 at 19:16
@andrea-f Why ? – melpomene Nov 21 '18 at 19:17
1

maybe you have a look to the [comma operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Comma_Operator). – Nina Scholz Nov 21 '18 at 19:19
1

@NinaScholz That does not fully answer the question. Please read it in full. - *"Somehow the second function is the one that is being returned, but what part of the code is actually executing it?"* – Spencer Wieczorek Nov 21 '18 at 19:23
There are some answers about the comma operand, but the main question here is the other part - execution of the inner function – Yozex Nov 21 '18 at 19:23
@Yozex I will write up an answer and link you to it, if this doesn't get reopened – mhodges Nov 21 '18 at 19:24
There is no "outer" and "inner". There are two functions (operands of the comma operator), and the comma operator returns one of them. – melpomene Nov 21 '18 at 19:26
@Yozex [Here's an explanation for now](https://repl.it/@ugam44/KhakiUpsetMatch) – mhodges Nov 21 '18 at 19:27
@Yozex The comma makes it so only the last function is returned. The `()` at the end of `var f = (..)()` is what executes the function `g`. That makes `f` the value of `2` and is a number. – Spencer Wieczorek Nov 21 '18 at 19:28
https://stackoverflow.com/questions/8228281/what-is-the-function-construct-in-javascript – Teemu Nov 21 '18 at 19:30
Thank you for your effort, I think I got it! – Yozex Nov 21 '18 at 19:30

Which part of the code executes inner function?

0 Answers0