# What does the double negation operator !! do in JavaScript?

> Learn what the double negation operator !! does in JavaScript: it is two negations that coerce any value into its boolean equivalent, true or false.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2019-09-01 | Topics: [JavaScript](https://flaviocopes.com/tags/js/) | Canonical: https://flaviocopes.com/javascript-double-negation-operator/

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](https://flaviocopes.com/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`.