Permutations in JavaScript?

Question

I\'m trying to write a function that does the following:

• takes an array of integers as an argument (e.g. [1,2,3,4])
• creates an array of all the possib

Answer 1

Some version inspired from Haskell:

perms [] = [[]]
perms xs = [ x:ps | x <- xs , ps <- perms ( xs\\[x] ) ]

function perms(xs) {
  if (!xs.length) return [[]];
  return xs.flatMap(x => {
    // get permutations of xs without x, then prepend x to each
    return perms(xs.filter(v => v!==x)).map(vs => [x, ...vs]);
  });
}
document.write(JSON.stringify(perms([1,2,3])));