Algorithme qui recherche un doublon dans un tableau

doublon.js

let score = [10,2,3,3,2];
let doublon = [];
for (let i = 0; i < score.length; i++) {
    var temp = score[i];
    for (let j = i+1; j < score.length; j++) {
        if (temp === score[j]) {
            doublon.push(temp)
        }
    }
}

console.log(doublon);

doublon1.js

const arr = [12,12,102,12]
const clone = [];
arr.forEach(function(x){
    if (clone.includes(x) === false) {
        clone.push(x);
    }

})
console.log(clone)