challenge-34.js

let arr = [1, 1, 1, 2, 3, 4, 3];

let uniqueElements1 = [...new Set(arr)];
console.log(uniqueElements1); // [1, 2, 3, 4]

let uniqueElements2 = arr.filter((ele, i) => i === arr.indexOf(ele));
console.log(uniqueElements2); // [1, 2, 3, 4]

let uniqueElements3 = arr.reduce((acc, curr) => {
  if (!acc.includes(curr)) acc.push(curr);
  return acc;
}, []);
console.log(uniqueElements3); // [1, 2, 3, 4]

let uniqueElements4 = [];
for (let i = 0; i < arr.length; i++) {
  if (!uniqueElements4.includes(arr[i])) uniqueElements4.push(arr[i]);
}
console.log(uniqueElements4); // [1, 2, 3, 4]

// Bonus (Faster)
let uniqueElements5 = [];
let seen = {};
for (let i = 0; i < arr.length; i++) {
  if (!seen[arr[i]]) {
    seen[arr[i]] = true;
    uniqueElements5.push(arr[i]);
  }
}
console.log(uniqueElements5); // [1, 2, 3, 4]