How can I create all combinations of this object's keys/values in JavaScript?

Question

I have the following JavaScript object structure:

var options = {
    optionOne: [true, false],
    optionTwo: [true, false],
    optionThree: [
        null,
        {property1: 9, property2: 7},
        {property1: 4, property2: 12},
        {property1: 16, property2: 14}
    ]
};

Please note that the number of key/pairs in this object will differ. So there might actually be optionFour, optionFive, etc., and each option can have any number or type of values for its array.

I need to iterate through this object and create an array containing objects of all possible option combinations:

[
    {optionOne: true,  optionTwo, true,  optionThree: null},
    {optionOne: false, optionTwo, true,  optionThree: null},
    {optionOne: true,  optionTwo, false, optionThree: null},
    {optionOne: false, optionTwo, false, optionThree: null},
    {optionOne: true,  optionTwo, true,  optionThree: {property1: 9, property2: 7}},
    {optionOne: false, optionTwo, true,  optionThree: {property1: 9, property2: 7}},
    {optionOne: true,  optionTwo, false, optionThree: {property1: 9, property2: 7}},
    {optionOne: false, optionTwo, false, optionThree: {property1: 9, property2: 7}},
    {optionOne: true,  optionTwo, true,  optionThree: {property1: 4, property2: 12}},
    {optionOne: false, optionTwo, true,  optionThree: {property1: 4, property2: 12}},
    {optionOne: true,  optionTwo, false, optionThree: {property1: 4, property2: 12}},
    {optionOne: false, optionTwo, false, optionThree: {property1: 4, property2: 12}},
    {optionOne: true,  optionTwo, true,  optionThree: {property1: 16, property2: 14}},
    {optionOne: false, optionTwo, true,  optionThree: {property1: 16, property2: 14}},
    {optionOne: true,  optionTwo, false, optionThree: {property1: 16, property2: 14}},
    {optionOne: false, optionTwo, false, optionThree: {property1: 16, property2: 14}}
]

I'm struggling on how to accomplish this but am fairly confident the answer lies in recursion.

Can the algorithm gods help me?

how about this - http://stackoverflow.com/questions/4331092/finding-all-combinations-of-javascript-array-values — Joe Hanink, Sep 29 '15 at 08:10
HA -- that's *exactly* the one I've been looking at for the past hour and trying to model :) — Chad Johnson, Sep 29 '15 at 08:12

Dmytro Shevchenko · Accepted Answer · 2016-10-24T12:08:22.497

15

function getCombinations(options, optionIndex, results, current) {
    var allKeys = Object.keys(options);
    var optionKey = allKeys[optionIndex];

    var vals = options[optionKey];

    for (var i = 0; i < vals.length; i++) {
        current[optionKey] = vals[i];

        if (optionIndex + 1 < allKeys.length) {
            getCombinations(options, optionIndex + 1, results, current);
        } else {
            // The easiest way to clone an object.
            var res = JSON.parse(JSON.stringify(current));
            results.push(res);
        }
    }

    return results;
}

Use it like this:

var results = getCombinations(options, 0, [], {});

Here's a working JSFiddle example.

edited Oct 24 '16 at 12:08

answered Sep 29 '15 at 08:35

Dmytro Shevchenko

33,431
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@ChadJohnson I would also wrap this into a class for better usability. Then you'd be able to use it like this: `(new Permuter(options)).getPermutations()`. Or something similar where you don't have to pass in base recursion values. – Dmytro Shevchenko Sep 29 '15 at 08:43
1

Thank you sir. I hope all is well with you and your family there in Ukraine! – Chad Johnson Sep 29 '15 at 08:45
1

Nice solution! One minor suggestion would be to add default parameter values so that we can call the method by passing the object only. – Nicolas Bouvrette Sep 22 '19 at 22:30
Thank you. You are life saver – Janak Prajapati Aug 26 '20 at 09:16

score 2 · Answer 2 · answered Mar 05 '21 at 01:58

This was recently resurrected, and I think modern JS offers a cleaner way to write this.

const crossproduct = (xss) => 
  xss.reduce((xs, ys) => xs.flatMap(x => ys.map(y => [...x, y])), [[]])

const combinations = (o, keys = Object .keys (o), vals = Object .values (o)) =>
  crossproduct(vals).map(xs => Object.fromEntries(xs.map ((x, i) => [keys[i], x])))


const options = {optionOne: [true, false], optionTwo: [true, false], optionThree: [null, {property1: 9, property2: 7}, {property1: 4, property2: 12}, {property1: 16, property2: 14}]}

console .log (JSON .stringify (
  combinations (options)
, null, 4))

.as-console-wrapper {max-height: 100% !important; top: 0}

We start with a crossproduct function which, for instance, takes

[[1, 2], ['a', 'b', 'c'], ['T', 'F']]

and returns

[
  [1, 'a', 'T'], [1, 'a', 'F'], [1, 'b', 'T'], [1, 'b', 'F'], [1, 'c', 'T'], [1, 'c', 'F'], 
  [2, 'a', 'T'], [2, 'a', 'F'], [2, 'b', 'T'], [2, 'b', 'F'], [2, 'c', 'T'], [2, 'c', 'F']
]

Then combinations takes our object apart with Object.keys, and Object.values, passes the values to crossproduct, then for each array in the result, maps over the values, associating the corresponding key with each, then rehydrating an object with Object.fromEntries.

This order is what seems like the logical order of results to me. But if we swapped out the returned expression for crossproduct with the following, we would get the order mentioned in the question:

  xss .reduce ((xs, ys) => ys .flatMap (y => xs .map (x => [...x, y])), [[]])

Manuel · Answer 3 · 2021-03-04T22:29:02.987

Here is an improvement, based on Dmytro's answer:

function getPermutations(object, index = 0, current = {}, results = []) {
  const keys = Object.keys(object);
  const key = keys[index];
  const values = object[key];

  for (const value of values) {
    current[key] = value;
    const nextIndex = index + 1;

    if (nextIndex < keys.length) {
      this.getPermutations(object, nextIndex, current, results);
    } else {
      const result = Object.assign({}, current);
      results.push(result);
    }
  }
  return results;
}

Improvements:

Works for any kind of value, even if the value is a function
Default argument values, can be easily invoked with: const p = getPermutations(object);
Minor semantic improvements

How can I create all combinations of this object's keys/values in JavaScript?

3 Answers3

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