Javascript self executing function “is not a function”

I have:

var Init = (function() {
   my js goes here

And my js executes correctly when the page is loaded. I also have:

$('form :checkbox').change(function() {

But firebug says Init is not a function.

It isn’t a function.

(function() {

evaluates the anonymous function right then. And the result of the evaluation apparently does not return a function-object in this case 🙂


f = (function() {
   return "not a function :("


f = (function() {
   return function () { return "Yay!" }

Happy coding 🙂

Here is a function which will “execute something once” and then “return that something to execute later”. (See “You can either [assign] a function or call it; you can’t do both…” from Slaks answer.) However, I wouldn’t do it like this.

Init = (function () {
  function Init () {
  return Init

Here is another solution (much shorter/cleaner) from CD Sanchez (see comment) which takes advantage of the fact that an assignment evaluates to the assigned value:

var Init; (Init = function Init () {
  alert ("wee");

In order for Init to execute as a function, your code within the self-executing function must return a function, and the only reason to do this is if you need to construct a specific function dynamically dependent upon some data states:

var Init = (function() {

    // some code

    return function () {
        // some dynamic code dependent upon your previous code


Init isn’t a function; it’s the result of calling the function.

You can either create a function or call it; you can’t do both at once.

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Technically, you could fix that by adding return arguments.callee; to return the function from the call.
However, that’s a dumb idea.

You probably shouldn’t be calling the function; you need to understand what you want your code to do.

Quick one
Try replacing like this

var Init = function() {
   my js goes here

and on load call Init

you could do as above, but you could also do

function Init(){...}(); 

There’s nothing to stop you from having a named self-executing function.
If you want to avoid having a function named Init, you can do as CD Sanchez suggested and assign it in the execution.

The (); at the end makes it self executing. Wrapping the function in parentheses makes it anonymous. But it seems that you don’t want it to be anonymous.

You may try declaring it this way:

(function Init(){ 

But this will reduce usage of this function into it’s body

Other way is to separate declaration from execution:

var Init = function(){
    initResult = (function(){ return Init(); })();

The answers/resolutions are collected from stackoverflow, are licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 .

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