Cartesian Product

javascript-cartesian-product.js

/* 
https://en.wikipedia.org/wiki/Cartesian_product

In set theory (and, usually, in other parts of mathematics), a Cartesian product is a mathematical 
operation that returns a set (or product set or simply product) from multiple sets. That is, for sets A and B, 
the Cartesian product A × B is the set of all ordered pairs (a, b) where a ∈ A and b ∈ B. Products can 
be specified using set-builder notation, e.g.

*/
let A = ['x', 'y' , 'z']
let B = [1, 2, 3, 4]

const cartesianProduct = (a, b) => {
  const result = Array(a.length).fill(null).map(() => Array(b.length).fill(null))
  for (let i = 0; i < a.length; i++) {
    for (let j = 0; j < b.length; j++) {
      result[i][j] = a[i] + ',' + b[j]
    }
  }
  return result
}