Set variables out of anonymous functions in Javascript

Question

I am trying to get a value outside of an anonymous function in Javascript. Basically, I want this function to return 4. I feel like there is an easy fix but I am unsure. Thanks!

function a(){
  var x = 1;
  ()=>{
    x = 4;
  }
  return x;
}

The anonymous function is never called. But why would you use one at all instead of simply `return 4`? Please post your actual code. — Bergi, Jul 09 '17 at 22:11

score 5 · Accepted Answer · answered Jul 09 '17 at 22:13

You have to invoke the inner function, but since it's anonymous, it has to become an immediately invoked function expression. And, since there is only one statement in the anonymous function, you can omit the curly braces if you like.

function a(){
  var x = 1;
  (() => x = 4)();
  return x;
}

console.log(a());

Alex McMillan · Answer 2 · 2017-07-09T22:20:07.967

1

Your example defines a function, but nothing is running it. Perhaps try using an IIFE:

function a(){
  var x = 1;
  (()=>{
    x = 4;
  })();
  return x;
}

edited Jul 09 '17 at 22:20

answered Jul 09 '17 at 22:13

Alex McMillan

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The last set of parenthesis ()` should be on the outside otherwise you'll get an error. – Khauri Jul 09 '17 at 22:16
Thanks, updated. This was never the case before fat arrow syntax ;) – Alex McMillan Jul 09 '17 at 22:20

score 1 · Answer 3 · answered Jul 09 '17 at 22:13

Pretty weird that you'd want to do this, but just make sure you call the inner function. This can be done using the Immediately-invoked function expression syntax.

function a(){
  var x = 1;
  (()=>{
    x = 4;
  })()
  return x;
}

console.log(a());

Set variables out of anonymous functions in Javascript

3 Answers3