Unique elements of JavaScript 2D array. If there are duplicates, how to remove them all?

Question

I have array of arrays called user_list that looks something like this:

[[user3, 12], [user2, 10], [user1, 5], [user5, 5], [user4, 4]]

First column contains usernames and second their balance. I've already sorted them by balance, and now I have to remove all rows that have same balance and add users that have different balance to new array called unique_user_list.

So, expected result is:

[[user3, 12], [user2, 10], [user4, 4]]

Here's my loop (that doesn't work).

for(var i = 0; i<user_list.length; i++) {
    var unique = user_list[i][1];
    for(var j = 1; j<user_list.length; j++) {
        if(unique!=user_list[j][1]) {
            unique_user_list[i] = user_list[i][0];
        }
    }
}

Would you be fine with splicing the elements from the original array? I fell that doing this would make it simpler. — Kevin Wang
– Kevin Wang, Commented Feb 14, 2016 at 16:09
@KevinWang: Could you please be more specific or show me example? I'm totally new to JavaScript. — matejcro
– matejcro, Commented Feb 14, 2016 at 16:22
There is a way that you can remove the elements from the array, and with this method you can just remove all elements from the user_list that have duplicate balances. — Kevin Wang
– Kevin Wang, Commented Feb 14, 2016 at 16:27

sco_tt · Accepted Answer · 2016-02-14 16:38:54Z

1

There's probably a better way to do this, but you can make it work like this:

function getUnique() {
  var unique_user_list = [];
  for (var i = 0; i < user_list.length; i++) {
    var unique = user_list[i][1];
    var match = false;
    for (var j = 0; j < user_list.length; j++) {
      if (unique == user_list[j][1] && j != i) {
        match = true;
      }
    }
    if (!match) {
      unique_user_list.push(user_list[i]);
    }
  }
  return unique_user_list;
}

You want to make sure j != i, so you're not checking the value equals itself. And you want to push to your output array in the outer loop for the same reason.

https://jsfiddle.net/sco_tt/w704p6kt/

edited Feb 14, 2016 at 16:38

answered Feb 14, 2016 at 16:25

sco_tt

3031 silver badge8 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Nina Scholz · Accepted Answer · 2016-02-14 17:09:12Z

0

This solution features Array#filter() for the filtering of the balances with a single loop only.

var data = [['user3', 12], ['user2', 10], ['user1', 5], ['user5', 5], ['user4', 4]],
    lastBalance,
    filtered = data.filter(function (a, i, aa) {
        if (i + 1 < aa.length && a[1] === aa[i + 1][1]) {
            lastBalance = a[1];
            return false;
        }
        return a[1] !== lastBalance;
    });

document.write('<pre>' + JSON.stringify(filtered, 0, 4) + '</pre>');

edited Feb 14, 2016 at 17:09

answered Feb 14, 2016 at 16:43

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

Collectives™ on Stack Overflow

Unique elements of JavaScript 2D array. If there are duplicates, how to remove them all?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related