What is the purpose of the double negation operator !! in JavaScript?

The double negation operator !! is commonly used in JavaScript. But what does it actually do?

When you have an expression that returns a result, you may want to convert that result into a boolean value - either true or false.

The !! operator achieves this conversion. It consists of two negation operators (!) applied consecutively to the result of the expression. Although there is no specific !! operator in JavaScript, this sequence of negations accomplishes the desired outcome.

First, the operator negates the original result, and then it negates it again. This process guarantees that any truthy value, such as a non-zero number, a string, an object, or an array, will be converted to true. On the other hand, falsy values like 0, an empty string, undefined, or NaN will be converted to false.

In conclusion, the purpose of the double negation operator !! is to ensure that the result of an expression is converted into a boolean value, facilitating clearer and more concise logic in your JavaScript code.