What does the ! part of !function(){...}(); mean?

Question

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What does the exclamation mark do before the function?

So I've come across the use of the following by the twitter share button code:

!function (d, s, id) {
    var js, fjs = d.getElementsByTagName(s)[0];
    if (!d.getElementById(id)) {
        js = d.createElement(s);
        js.id = id;
        js.src = "//platform.twitter.com/widgets.js";
        fjs.parentNode.insertBefore(js, fjs);
    }
}(document, "script", "twitter-wjs");

And I was just wondering what the !function bit does.

I'm guessing is short for (function(){...})(); but I couldn't find anything online to confirm it.

@Quentin ah thanks, I had a search but of course searching for "!function" doesn't help do much :/ — Samuel Parkinson, Oct 04 '12 at 11:06

Nate Higgins · Accepted Answer · 2012-10-04T11:26:40.433

3

While @elias-van-ootegem got it mostly right, many browsers will consider it a syntax error without the bang.

function() { ... }() // Bad
!function() { ... }() // Good
(function() { ... })() // Better, more readable.
(function() { ... }()) // Best

edited Oct 04 '12 at 11:26

answered Oct 04 '12 at 11:02

Nate Higgins

2,104
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`(function() { ... }())` even better :) – Fabrizio Calderan Oct 04 '12 at 11:03
see http://stackoverflow.com/a/12259808/1098851 last paragraph – Fabrizio Calderan Oct 04 '12 at 11:06
@NatIsGleek thanks very much! Useful to see all the ways and their ranking. – Samuel Parkinson Oct 04 '12 at 11:08
@NatIsGleek: Which browsers consider it a SyntaxError with the `!`? Please name at least one. – I Hate Lazy Oct 04 '12 at 11:14
1

Sorry, that was supposed to say without @user1689607 – Nate Higgins Oct 04 '12 at 11:26

What does the ! part of !function(){...}(); mean?

1 Answers1