Given an input string, return all possible permutations of the string.

1-string-permutations.js

function swap(word, i, j) {
  let swapIndex = word.split("");
  let temp = swapIndex[j];
  swapIndex[j] = swapIndex[i];
  swapIndex[i] = temp;
  return swapIndex.join("");
}

function permuteStringRec(word, pointer, result) {
  // pointer is a number indication an index of a character in the string
  // everything to the left from the pointer is "fixed" (we don't swap it or touch in any way)
  // if pointer points to the last character, there is nothing left to swap, so it's the base case
  if (pointer === word.length - 1) {
    result.push(word);
  }
  // otherwise, repeatedly swap character at pointer with every character after pointer
  // and call the same function recursively with the swapped word, but with incremented pointer
  // so for example in case of word=xyz it will give us
  // initial call: word=xyz, pointer=0 (0 will be swapped with 0, 1 and 2)
  // it will produce 3 following recursive calls:
  // word=xyz pointer=1, word=yxz pointer=1, word=zyx pointer=1
  // in all those 3 cases, the first character is "fixed", and only 2 last characters are swapped
  // this way our recursive calls cover all the permutations
  for (let i = pointer; i < word.length; ++i) {
    permuteStringRec(swap(word, pointer, i), pointer + 1, result);
  }
}

export function permuteWord(word) {
  let result = [];
  permuteStringRec(word, 0, result);
  return result;
}

2-README.md