What is Double Exclamation Marks in Javascript Mean?

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In some Javascript code, you might see the use of a double exclamation marks such as …

myAnswer = !! myVariable;

What does the double exclamation mark mean?  Is there even such an operator in Javascript?

Actually, it is two operators right next to each other.  Think of it as …

myAnswer = ! ( ! myVariable)

Now you can see that it is two negation operators (or “not” operators).  The negation operator returns a boolean.  The first negation operator converts myVariable to boolean.  But then you need the second negation operator to reverse the first negation.

So effectively, the double exclamation converts objects into boolean.

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