JavaScript !function(){}

2018-06-05 12:06:36

This question already has an answer here:

What does the exclamation mark do before the function? 9 answers

!function(a){/* ... */}();

Using an unary operator to invoke an IIFE is common practice. That's a common shorthand for:

(function(a){/* ... */}());

or:

(function(a){/* ... */})();

You can also substitute the not unary operator with any other unary operator:

-function(a){ /* ... */ }();
+function(a){ /* ... */ }();
/* ... etc. */

gives a good explaination for function invocation https://github.com/airbnb/javascript/issues/44#issuecomment-13063933

!function () {}();

is equivalent to

(function(){})();

except the author is saving 1 byte of code.

In many cases, it's about saving bytes.

!function aaa(){}()
!function bbb(){}();

is the same as this:

!function aaa(){}()
;(function bbb(){})();

notice the ";" in that last bit. That is defensive, as it protects your code a bit from runaway js that might preceed it.

funny, I asked this same question some time ago:

Came across a convention I've never seen. What does it do? !function

great reference on it: What does the exclamation mark do before the function?

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