Javascript most efficient way to combine array elements with each other

Question

I'm trying to combine arrays of string with unique combinations, like 'Mark|Tom' but without 'Tom|Mark'

I have written this code:

let arr = ['Tom', 'Danny', 'Mark']
let sets = []

for (let i = 0; i < arr.length; i++) {
  let others = arr.filter(name => name != arr[i])
  others.forEach((other) => {

    let newel = arr[i] + '|' + other
    let test = newel.split('|')
    if (sets.includes(test[1] + '|' + test[0]) || sets.includes(newel)) return

    sets.push(newel)
  })

}

console.log(sets)

This is iterating through every array element and then creating another array of other elements from basic array and then iterating through them (again iteration), creating a combination, checking if there is reversed combination of our elements (if this was created in previous loops) and if there is no such combination = push it to target array.

Is there more elegant way to do that task?

can you post what is desired output ? also why it should be Mark|Tom not Tom|Mark ? — Code Maniac
– Code Maniac, Commented Sep 16, 2019 at 1:16
just run code snippet It's irrelevant if it's Mark|Tom or Tom|Mark, it has to be unique combination — KrystianK
– KrystianK, Commented Sep 16, 2019 at 1:18
Output your code showing is doesn't matches with logic, so it will be better to desired result, You want to Tony|Dany|Mark also to be in output ? — Code Maniac
– Code Maniac, Commented Sep 16, 2019 at 1:23

Code Maniac · Accepted Answer · 2019-09-16 01:39:50Z

3

what about this one:

const arr = ['Tom', 'Danny', 'Mark'];
const sets = [];

for (let i = 0; i < arr.length; i++) {
  for (let j = i + 1; j < arr.length; j++) {
    sets.push(arr[i] + '|' + arr[j]);
  }
}

console.log(sets);

Also you can make arr unique before start the calculate:

const arr = [...new Set(['Tom', 'Danny', 'Mark', 'Tom'])]; // ['Tom', 'Danny', 'Mark']

edited Sep 16, 2019 at 1:39

Code Maniac

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answered Sep 16, 2019 at 1:20

n8o

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3 Comments

Code Maniac Over a year ago

You can create a running snippet on SO mate, how to create a running snippet

n8o Over a year ago

@CodeManiac Ahhh thank you very much! I was looking for it :)

Code Maniac Over a year ago

Always welcome, anyways good answer and probably the most efficient one +1

Nick Parsons · Accepted Answer · 2019-09-16 01:26:05Z

2

I would make your array a set so it will remove all duplicates initially like so:

new Set(['Tom', 'Danny', 'Mark']);

Now, you can pair the i^th element with all elements up to the n^th element using .flatMap and .reduce like so:

const name_arr = Array.from(new Set(['Tom', 'Danny', 'Mark']));
const res = name_arr.flatMap(
  (name, i) => name_arr.slice(i+1).reduce((a, n) => [...a, name+'|'+n],[])
);

console.log(res);

answered Sep 16, 2019 at 1:26

Nick Parsons

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Comments

Code Maniac · Accepted Answer · 2019-09-16 01:37:21Z

1

You can create a Set of passed array, loop through the array, for each index get the array after that index and loop thorough this other array and build combinations

let arr = ['Tom', 'Danny', 'Mark']

const uniqueCombo = (arr) => {
  let newSet = [...new Set(arr)]
  return newSet.reduce((op, inp, index) => {
    newSet.slice(index + 1,).forEach(v => {
      op.push(inp + '|' + v)
    })
    return op
  },[])
}

console.log(uniqueCombo(arr))
console.log(uniqueCombo(['A', 'B', 'A', 'C', 'D']))
console.log(uniqueCombo(['A', 'B', 'A', 'C']))

edited Sep 16, 2019 at 1:37

answered Sep 16, 2019 at 1:21

Code Maniac

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Comments

Joven28 · Accepted Answer · 2019-09-16 01:30:50Z

0

Try this one. This approach filters out the index which has been previously used to push item to array.

const arr = ['Tom', 'Danny', 'Mark'];

const comb = [];
for (let i = 0; i < arr.length; i++) {
  for (j = i + 1; j < arr.length; j++) {
    comb.push(arr[i] + '|' + arr[j]);
  }
}
console.log(comb);

edited Sep 16, 2019 at 1:30

answered Sep 16, 2019 at 1:25

Joven28

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