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JS Coding Question #4: Remove Duplicates [Common Question]

Interview Question #4:

Write a function that will remove duplicate in an arrayβ“πŸ€” You can get a variation of this question as Get unique characters from a list.

If you need practice, try to solve this on your own. I have included 2 potential solutions below.

Note: There are many other potential solutions to this problem.

Feel free to bookmark πŸ”– even if you don't need this for now. You may need to refresh/review down the road when it is time for you to look for a new role.


Solution #1: ES6 Set

  • uses the elegance of Set just like other programming languages. A value in the Set may only occur once; it is unique in the Set's collection.
function removeDuplicates(array) {
  return [ Set(array)]
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Solution #2: Object

  • below will use a js plain object to store key value pairs. Value can be other values as well, i chose to increment it so we may use it for other purpose like get the total count for a characters, etc.
function removeDuplicates(array) {
  const map = {}

  for (const char of array) {
    if (map[char]) {
    } else {
       map[char] = 1

  return Object.keys(map)
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