Permutation https://en.wikipedia.org/wiki/Permutation

permutation.js

/**
 * Generate set of permutations for given length.
 */
function* permute(len) {
  if (len <= 0 || len > 10) throw "argument must be in range 0..10";

  function* go(n, permutation, members) {
    if (n === 0) {
      yield permutation;
    } else {
      for (let index = 0; index < members.length; index++) {
        const member = members[index];
        const rest = members.filter((_, _index) => _index !== index);
        yield* go(n - 1, [...permutation, member], rest);
      }
    }
  }

  yield* go(
    len,
    [],
    new Array(len).fill(0).map((_, index) => index) // [0, 1, 2]
  );
}

const s = "rgb";
for (const permutation of permute(s.length)) {
  console.log(permutation.map((i) => s[i]).join(""));
}
// Will output:
// rgb
// rbg
// grb
// gbr
// brg
// bgr