All permutations of a string

function getAllPermutations(string) {
  let results = [];

  if (string.length === 1) {
    results.push(string);
    return results;
  }

  for (let i = 0; i < string.length; i++) {
    let firstChar = string[i];
    let charsLeft = string.substring(0, i) + string.substring(i + 1);
    let innerPermutations = getAllPermutations(charsLeft);
    for (let j = 0; j < innerPermutations.length; j++) {
      results.push(firstChar + innerPermutations[j]);
    }
  }
  return results;
}