You might find the `!!` operator used in the wild. What does it mean?
Suppose you have an expression, which gives you a result.
You want this result to be a boolean. Either true
or false
.
Not a string, 0, an empty string, undefined, NaN or whatever. true
or false
.
The !!
operator does that.
And in reality it’s two negation operators one after the other. There’s no !!
operator in JavaScript. But there’s !
.
It first negates the result of the expression, then it negates it again. In this way if you had a non-zero number, a string, an object, an array, or anything that’s truthy, you’ll get true
back.
Otherwise you’ll get false
.