Javascript: Find and delete all repeated items

Question

I have an array with the following elements:

A
B
B
C
B

If an item appears more than once, I have to delete all its occurrences. Therefore, it would be like this:

A
C

I have found lots of examples on how to remove the other repeated elements but still leave the "original" one, out of that I couldn't find anything closer to it and I am really lost.

I have thought about saving in a object the following: 1. The item's value; 2. How many times it appears; 3. The position of all the appearances.

If the times appeared was more than 1, I would remove all of the following positions in the array. Is it a good idea? What would be the best way to do it?

Thank you very much!

To clarify, you only want to modify the original array, not create a new one with the elements from the original array removed? — Daryl, Dec 05 '16 at 18:24
One way could be to create a new array and only push original values by check if value already exists in the new array. Maybe not the best solution, but is one way :P — Medda86, Dec 05 '16 at 18:25

score 9 · Accepted Answer · answered Dec 05 '16 at 18:25

9

You can do this using filter() and return only unique elements by checking if indexOf is equal to lastIndexOf

var ar = ['A', 'B', 'B', 'C', 'B'];
var result = ar.filter(function(e) {
  return ar.indexOf(e) == ar.lastIndexOf(e);
})

console.log(result)

answered Dec 05 '16 at 18:25

Nenad Vracar

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@Nenad, Nice! And instead of `ar.indexOf(e)` you could use the current index that `filter` already give us, on its second parameter, to compare against `ar.lastIndexOf(e)`. The signature is `filter(element, index, array)` – Diego ZoracKy Dec 05 '16 at 18:35
the callback is not reusable. – Nina Scholz Dec 05 '16 at 18:37
@PossessWithin You're welcome. – Nenad Vracar Dec 05 '16 at 18:39
Even though this answer looks cool it does tons of `lastIndexOf()` operation. Best would be to use a hash and filter for value 1. – Redu Dec 05 '16 at 18:43

Javascript: Find and delete *all* repeated items

1 Answers1

Javascript: Find and delete all repeated items