Create new array from existing array with unique joined values from existing array

Question

Does anyone know how I can create a new array from existing array with unique joined values from existing array?

const originalArray = [
  [
    { value: 'red', id: 99 },
    { value: 'blue', id: 100 },
  ],
  [
    { value: 'small', id: 101 },
    { value: 'medium', id: 102 },
  ],
  [
    { value: 'modern', id: 103 },
    { value: 'classic', id: 104 },
  ],
];
//
//
const newArrayBasedOnOriginalArray = [
  { value: 'red/small/modern' },
  { value: 'red/small/classic' },
  { value: 'red/medium/modern' },
  { value: 'red/medium/classic' },
  { value: 'blue/small/modern' },
  { value: 'blue/small/classic' },
  { value: 'blue/medium/modern' },
  { value: 'blue/medium/classic' },
];

I calculated that the length of the new array should always be as following:

// length of new array
const lengthOfNewArray = originalArray
  .map((value) => {
    return value.length;
  })
  .reduce((current, old) => {
    return current * old;
  });
//
//
console.log('length of new array:', lengthOfNewArray); // 8

You can also have a look at this module I made a bunch of years ago: npmjs.com/package/combinatorial-explosion — Pier Paolo Ramon
– Pier Paolo Ramon, Commented Aug 12, 2022 at 10:01

RenaudC5 · Accepted Answer · 2022-08-12 08:30:48Z

3

You can do it recursively

const originalArray = [
  [
    { value: 'red', id: 99 },
    { value: 'blue', id: 100 },
  ],
  [
    { value: 'small', id: 101 },
    { value: 'medium', id: 102 },
  ],
  [
    { value: 'modern', id: 103 },
    { value: 'classic', id: 104 },
  ],
];

const getPossibleCombination = (currentValue, arraysRemaining) => {
  if(arraysRemaining.length === 0) return currentValue

  const values = []
  
  const firstArray = arraysRemaining[0]
  
  firstArray.forEach(({value}) => {
    values.push(getPossibleCombination(`${currentValue}/${value}`, arraysRemaining.slice(1, arraysRemaining.length)))
  })
  
  return values.flat()
}

const values = getPossibleCombination('', originalArray)
console.log(values)

answered Aug 12, 2022 at 8:30

RenaudC5

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Comments

Marco Luzzara · Accepted Answer · 2022-08-12 09:23:40Z

3

In this case, you do not necessarily need recursion. Array.reduce() greatly does the job:

const originalArray = [
  [
    { value: 'red', id: 99 },
    { value: 'blue', id: 100 },
  ],
  [
    { value: 'small', id: 101 },
    { value: 'medium', id: 102 },
  ],
  [
    { value: 'modern', id: 103 },
    { value: 'classic', id: 104 },
  ],
];

const newArray = originalArray
  .map(elem => elem.map(({value}) => value))
  .reduce((acc, cur) => acc.flatMap(seq => cur.map(part => `${seq}/${part}`)))
  .map(elem => ({value: elem}))

console.log(newArray)

Aside from the initial and final map(), used to simplify the input objects, what I am doing is continuously combining the accumulator with the next sub-array.

For each object in the sub-array I duplicate every object in the accumulator, using the nested map(). flatMap() is used to keep the accumulator flat, with a simple map() the accumulator depth would increase every time we visit a new sub-array.

edited Aug 12, 2022 at 9:23

answered Aug 12, 2022 at 9:12

Marco Luzzara

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2 Comments

Qais Wardag Over a year ago

Your example works really good. However, I tried to make an if statement, if value already exist, then do not return or overwrite the existing value. ``` newArray = [{ value: 'red/small/modern', id: 1, price: 888 }]; ``` So, value "red/small/modern" already exist with price 888, I do not want to overwrite this value and the price. Could you help, to insert somekind of if statement for existing values?

Marco Luzzara Over a year ago

Glad you find it useful, please update the question with the new requirement. Don't forget to put the example and the expected result, thanks

mrafei · Accepted Answer · 2022-08-12 09:41:30Z

0

First of all if values in each of your arrays is unique then the concatenated values will be unique as well. After you make sure values are unique you can use this code to create combinations of strings:

const newArrayBasedOnOriginalArray = originalArray.reduce(
  (acc, el) =>
    el.flatMap(({ value }) =>
      acc.length ? acc.map((str) => str + "/" + value) : value
    ),
  []
).map(value=>({value});

edited Aug 12, 2022 at 9:41

answered Aug 12, 2022 at 9:11

mrafei

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