Javascript : Find Duplicate using set

const arr = [4, 2, 7, 4, 2, 8, 4, 9];

let set = new Set();

const duplicates = new Set();

for (let i = 0; i < arr.length; i++) {

if (set.has(arr[i])) {

    duplicates.add(arr[i]);

} else {

    set.add(arr[i]);    

}

}

console.log("Duplicates", Array.from(duplicates));

Output:

Duplicates [ 4, 2 ]

Explanation:

1. We first initialize an empty set called `set` to store the unique values from the array

and another empty set called `duplicates` to store the duplicate values.

2. We then loop through the array and check if the current number is already present in the

 `set` using the `has()` method. If it is present, we add it to the `duplicates` set using the

 `add()` method. If it is not present, we add it to the `set` using the `add()` method.

3. Finally, we log the `duplicates` set to the console, which contains all the duplicate

 values found in the original array. We convert the set to an array using `Array.from()`