What is an exclamation point in JavaScript?

Question

What does an exclamation mark before a function do?

Example:

return !loadDynamicBlock();

Dave Newton · Accepted Answer · 2011-11-26 15:18:38Z

A ! negates an expression.

In your example, if loadDynamicBlock() returned true, the function calling it would return false, and vice-versa: !true == false

It can also be used to create actual booleans from JavaScript's ideas of truthy and falsy.

var a = 5; !!(a - 5) === false; !!(a + 5) === true;

Peter Mortensen · Accepted Answer · 2023-09-12 13:42:37Z

8

The ! in JavaScript inverts a Boolean expression.

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answered Nov 4, 2011 at 15:51

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