Replace duplicates items in array with different values

Question

i would like to Replace duplicates items with different values.

eg arr = [1,1,1,1,2,2,2,3] i want to replace the duplicates with R

So the result looks like this arr = [1,R,R,R,2,R,R,3]

right now I'm using this approach:

    arr = [1,1,1,1,2,2,2,3]
    let previous = 0;
    let current = 1;
    while (current < arr.length) {
        if (arr[previous] === arr[current]) {
            arr[current] = 'R';
            current += 1;
        } else if (arr[previous] !== arr[current]) {
            previous = current;
            current += 1;
        }
    }

i wondering if there is different approach for to achieve that. for Example using Lodash (uniqwith, uniq).

Thanks

Keep a set or a map of everything you've encountered and when a duplicate is found, replace it. — VLAZ
– VLAZ, Commented Jul 21, 2020 at 14:02
do you want to replace only the same value in direct neighborhood? — Nina Scholz
– Nina Scholz, Commented Jul 21, 2020 at 14:05

jonatjano · Accepted Answer · 2020-07-21 14:29:22Z

2

here's how I'd do it It look if the current element is the first of the array with the current value and replace it if not

It may take some times on very big arrays

const input = [1,1,1,1,2,2,2,3]
let output = input.map(
  (el, i) => input.indexOf(el) === i ? el : 'R'
)
console.log(output)

edited Jul 21, 2020 at 14:29

answered Jul 21, 2020 at 14:05

jonatjano

3,7681 gold badge17 silver badges20 bronze badges

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

Comments

Nina Scholz · Accepted Answer · 2020-07-21 14:04:06Z

2

You could take a closure over a Set and check if the value is already seen or not.

let array = [1, 1, 1, 1, 2, 2, 2, 3],
    result = array.map((seen => v => seen.has(v) ? 'R' : (seen.add(v), v))(new Set));

console.log(...result);

A check previous value approach

let array = [1, 1, 1, 1, 2, 2, 2, 3],
    result = array.map((v, i, { [i - 1]: l }) => l === v ? 'R' : v);

console.log(...result);

answered Jul 21, 2020 at 14:04

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

1 Comment

Ernesto Stifano Over a year ago

Your solution is elegant, but I find it very, very hard to read (even with years of experience with JavaScript). I don't know how helpful it could be for someone who is just starting to learn.

Ernesto Stifano · Accepted Answer · 2020-07-21 14:05:51Z

1

This is actually very simple to do by using sets (Set).

const initialArray = [1,1,1,1,2,2,2,3];
const valuesSet = new Set();

const newArray = initialArray.map((value) => {
    if (valuesSet.has(value)) {
        return 'R';
    } else {
        valuesSet.add(value);
        return value;
    }
});

answered Jul 21, 2020 at 14:05

Ernesto Stifano

3,1301 gold badge13 silver badges21 bronze badges

Collectives™ on Stack Overflow

Replace duplicates items in array with different values

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related