List Pairs

Form pairs using all the elements in an array.

[1, 2, 4, 1, 3] //=> [ [ 1, 2 ],
                       [ 1, 4 ],
                       [ 1, 3 ],
                       [ 2, 4 ],
                       [ 2, 3 ],
                       [ 4, 3 ] ]

You can selectively choose whether to allow pairs formed from the same elements ([a, a]), whether to allow duplicates ([a, b] and [a, b]), or symmetric cases ([a, b] and [b, a]).

If the original array is an array of objects, the resulting array contains references to the originals.

Install

$ npm install list-pairs

Usage

Given an input array, the function uniquePairs generates pairs with all the unique combinations. The array can have any type.

const numbers = [1, 2, 3];
await uniquePairs(numbers);
//=> [ [ 1, 2 ], [ 1, 3 ], [ 2, 3 ] ]

const objects = [{ a: 1 }, { b: 2 }, { c: 3 }];
await uniquePairs(objects);
//=> [
//   [ { a: 1 }, { b: 2 } ],
//   [ { a: 1 }, { c: 3 } ],
//   [ { b: 2 }, { c: 3 } ]
//   ]

You can also have more control using the individual functions noSelf, noDuplicates, and noReverse.

Here is another example.

const numbers = [1, 1, 2];
const allPairs = await pair(numbers);
//=> [ [ 1, 1 ], [ 1, 1 ], [ 1, 2 ], [ 1, 1 ], [ 1, 1 ], [ 1, 2 ], [ 2, 1 ], [ 2, 1 ], [ 2, 2 ] ]

const noSelfPairs = noSelf(allPairs);
//=> [ [ 1, 2 ], [ 1, 2 ], [ 2, 1 ], [ 2, 1 ] ]

const noDuplicatePairs = noDuplicates(noSelfPairs);
//=> [ [ 1, 2 ], [ 2, 1 ] ]

const finalPairs = noReverse(noDuplicatePairs);
//=> [ [ 1, 2 ] ]

// This could have been achieved with a single call
await uniquePairs(numbers);
//=> [ [ 1, 2 ] ]

// ... or by concatenating the individual functions
await pair(numbers) //
  .then(noSelf)
  .then(noDuplicates)
  .then(noReverse);
//=> [ [ 1, 2 ] ]

Refer to this file for a working example.

License

MIT

Credits

Developed by MAKinteract with ♥️.