In JavaScript, the double exclamation mark (!!) is often used as a shorthand to convert a value to its corresponding Boolean representation. It essentially coerces a value to either true or false. Here's a quick explanation and example of its use:
 
Example:

let someValue = "Hello";
let isTruthy = !!someValue; 
console.log(isTruthy); // truesomeValue = 0;
let isFalsy = !!someValue; 
console.log(isFalsy); // false