Problem: We have a array of numbers. Calculate unique numbers in array

Solution 1:

const array = [1, 2, 1, 3, 2, 4, 5, 5]
const uniqueNumberChecker = {}
const uniqueNumbers = []

for(let i = 0; i <= array.length; ++i) {
  if (!uniqueNumberChecker[array[i]]) {
    uniqueNumbers.push(array[i])
    uniqueNumberChecker[array[i]] = true
  }
}

// Result uniqueNumbers

In above we use object to check number is exist of not, we can use Map type also

Solution 2:

const array = [1, 2, 1, 3, 2, 4, 5, 5]
const uniqueNumberSet = new Set(array)
const uniqueNumbers = Array.from(uniqueNumberSet)
// Or
const uniqueNumbers = [...uniqueNumberSet]

Two solutions have time complexity is O(n*logn)