JavaScript Trick: Exclamation Before Function

By Xah Lee. Date: . Last updated: .

What does that !function mean?



It is equivalent to this:


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

The exclamation is the boolean β€œnot” operator. [see JS: Boolean Operators]

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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