“`TypeError`: `[0,1]` is not a function” is thrown when using an IIFE

Question

Here is the code

var numberArray = [0, 1]

(function() {
  numberArray.push(2)

  function nestedFunction() {
    numberArray.push(3)

    function anotherNestedFunction() {
      numberArray.push(4)
    }

    console.log(numberArray)
  }
})()

I am expecting numberArray with value [0,1,2,3,4] but it is giving this error:

TypeError: [0,1] is not a function

Possible duplicate of [Immediately invoked function expression throws "object is not a function"](https://stackoverflow.com/questions/21031820/immediately-invoked-function-expression-throws-object-is-not-a-function) — Sebastian Simon, Aug 30 '18 at 08:53

Mamun · Accepted Answer · 2018-08-30T09:10:23.710

var numberArray = [0, 1]
(function() {

is equivalent to

var numberArray = [0, 1] (function() {

That is where the error rise.

To resolve the issue place ; after the array declaration which JavaScript engine will consider both the line as separate statement:

var numberArray = [0, 1];

(function() {
  numberArray.push(2);

  function nestedFunction() {
    numberArray.push(3);

    function anotherNestedFunction() {
      numberArray.push(4);
    }
    
    anotherNestedFunction();
    console.log(numberArray);
  }
  nestedFunction();
})();

To ignore all these unexpected issue, it is always good practice to use semicolons (;) after every statement in JavaScript.

Good to know why I'm using semicolons at the end of every line in JS :D (I just knew it could cause issues, but I've never seen an actual case of it) — d0n.key, Aug 30 '18 at 10:36

Orelsanpls · Answer 2 · 2018-08-30T09:02:47.397

Here is a working snippet

const numberArray = [0, 1];

(function() {
  numberArray.push(2);

  (function nestedFunction() {
    numberArray.push(3);

    (function anotherNestedFunction() {
      numberArray.push(4);
    })();

    console.log(numberArray);
  })();
})();

If you remove the ; after numberArray this is where you got a problem. You also have to use IIFE with your inner declared functions.

const numberArray = [0, 1]

(function() {
  numberArray.push(2);

  (function nestedFunction() {
    numberArray.push(3);

    (function anotherNestedFunction() {
      numberArray.push(4);
    })();

    console.log(numberArray);
  })();
})();

“`TypeError`: `[0,1]` is not a function” is thrown when using an IIFE

2 Answers2