JavaScript Trick: Exclamation Before Function

By Xah Lee. Date: . Last updated: .

What does that !function mean?

This:

!function(){}()

It is equivalent to this:

(function(){})()

It means, define a function expression, and evaluate it right there.

The exclamation is the boolean “not” operator. [see true, false]

The exclamation forces what follows into a expression.

People do this hack to save one character worth of source code file size.

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