Why can't this JS loop return a variable from inside the function

Question

With regards to the below code, I am trying to return a variable from inside of loop. I am calling the loop from inside of a function, however when the script is run I get "Uncaught ReferenceError: newVar is not defined".

Could someone explain why the value isn't being returned?

https://jsfiddle.net/95nxwxf4/

<p class="result"></p>

var testVar = [0,1,2];

var loopFunction = function loopFunction() {

    for (var j=0;j<testVar.length;j++) {
        if (testVar[j]===1) {
          var newVar = testVar[j];
          return newVar;
        }   
    }
    return false;
};

var privateFunction = (function privateFunction() {

  loopFunction();
  document.querySelector('.result').innerHTML = newVar;
})();

document.querySelector('.result').innerHTML =loopFunction(); — Gar
– Gar, Commented Jun 1, 2016 at 14:12
It is returned. But you are not doing anything with it: loopFunction();. eloquentjavascript.net/03_functions.html — Felix Kling
– Felix Kling, Commented Jun 1, 2016 at 14:13
FWIW, the IIFE is unnecessary as well as assigning to privateFunction (since the IIFE doesn't return anything). — Felix Kling
– Felix Kling, Commented Jun 1, 2016 at 14:16

bcr · Accepted Answer · 2016-06-01 14:11:52Z

3

You need to assign the value returned from loopFunction:

var privateFunction = (function privateFunction() {

  var newVar = loopFunction();
  document.querySelector('.result').innerHTML = newVar;
})();

Edit:

This is because the newVar assigned in loopFunction is scoped to that function, meaning it only exists inside that function.

answered Jun 1, 2016 at 14:11

bcr

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Comments

theDarse · Accepted Answer · 2016-06-01 14:23:23Z

0

newVar is not defined because the scope of the variable newVar is only defined in the loopFunction.

a value is in fact being returned for the loopFunction, but it is just that, a value, the variable newVar has fallen out of scope and as such is not defined in this line.

document.querySelector('.result').innerHTML = newVar;

change this to:

document.querySelector('.result').innerHTML = loopFunction();

answered Jun 1, 2016 at 14:23

theDarse

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