التحقق من وجود عنصر

const mySet = new Set([1, 2, 3, 4, 5]);

console.log(mySet.has(3)); // true
console.log(mySet.has(6)); // false

if (mySet.has(3)) {
  console.log("3 is in the set");
} else {
  console.log("3 is not in the set");
}

const mixedSet = new Set([1, '2', 3]);

console.log(mixedSet.has('1')); // false
console.log(mixedSet.has(2));  // false
console.log(mixedSet.has('2')); // true