IIFE inside for loop error VM531:3 Uncaught TypeError: console.log(...)

Question

this code doesn't work

for (let i = 0; i < 10; i++) {
  console.log("ddd")
  (function x() {
    console.log("eee")
  })();
}

VM531:3 Uncaught TypeError: console.log(...) is not a function at :3:3

these two works just fine

for (let i = 0; i < 10; i++) {
  (function x() {
    console.log("eee")
  })()
  console.log("ddd")
}

for (let i = 0; i < 10; i++) {
  (function x() {
    console.log("eee")
  })()
}

Add semi-colons to the end of your `console.log`'s and it will work. — Nick Parsons, Jun 13 '19 at 05:12

Jack Bashford · Accepted Answer · 2019-06-13T05:17:39.537

You need to have a semicolon after the console.log - otherwise it's trying to call the returned result of console.log (undefined) which isn't a function, which is calling your error.

Automatic semicolon insertion doesn't take into account whitespace.

for (let i = 0; i < 10; i++) {
  console.log("ddd");
  (function x() {
    console.log("eee")
  })();
}

Your code was trying to do:

console.log("ddd")(function x() {...})()

Which turns out to be:

undefined(function x() {...})()

Which results in your TypeError.

This problem of brackets overlapping due to a lack of semicolons is similar to my answer on this question.

IIFE inside for loop error VM531:3 Uncaught TypeError: console.log(...)

1 Answers1