javascript self executing syntax [duplicate]

Question

Did anyone know the code which define like this:

!function(window, undefined) { // do something } (window)

By searching in google, I can understand the syntax like:

function(window, undefined) { // do something } (window)

But I don't figure out any article about the syntax have "!" operator.

James Allardice · Accepted Answer · 2013-06-03 06:57:52Z

3

The ! operator is there so the function is parsed as an expression, rather than a declaration. Since a declaration cannot be invoked, your second example is a syntax error.

A more commonly seen form is to enclose the function in parentheses:

(function(window,undefined) { // do something }(window));

That has exactly the same effect, as does the use of any unary operator.

answered Jun 3, 2013 at 6:57

James Allardice

166k22 gold badges335 silver badges316 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

francisco.preller Over a year ago

I think you mean (function(window,undefined) { ... })(window);

CaptainCarl Over a year ago

I just came by this thread and was curious. By expression you mean like i.e an if statement? if (function()) {}?

Frederik.L Over a year ago

the exclamation mark transform the definition into an expression so that the parenthesis can call it right after because it has higher priority, !function(){}() is an evil version of (function(){})()

Edward · Accepted Answer · 2013-06-03 06:58:02Z

It might be like this.

!(function(window, undefined){ /* some code */ })(window); (function(window, undefined){ /* some code */ })(window);

Collectives™ on Stack Overflow

javascript self executing syntax [duplicate]

2 Answers 2

3 Comments

Comments

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

Comments

Linked

Related