Permutation in JavaScript

permutation.js

const Combinatorics = require('js-combinatorics');

const n = ['A', 'B', 'C', 'D'];
const k = 2;

const generator = Combinatorics.bigCombination(n, k);
const combinations = generator.toArray().length;

console.log(`Possible combinations: ${combinations}`); // "Possible combinations: 6"

let combination = undefined;
while (combination = generator.next()) {
  console.log(combination);
}

/**
 * [ 'A', 'B' ]
 * [ 'A', 'C' ]
 * [ 'A', 'D' ]
 * [ 'B', 'C' ]
 * [ 'B', 'D' ]
 * [ 'C', 'D' ]
 */