permutation.js

const permutation = text => {
  return permute("", text);
};
const permute = (prefix, sufix, arr = []) => {
  if (sufix.length == 0) arr.push(prefix);
  else {
    for (let i = 0; i < sufix.length; i++) {
      permute(
        prefix + sufix.charAt(i),
        sufix.substr(0, i) + sufix.substr(i + 1),
        //sufix.substr(0, i) + sufix.substr(i + 1, sufix.length),
        arr
      );
    }
  }
  return arr;
};
console.log(permutation("ABCD"));

const permutation = (arr) => {
  return permute([], arr);
};
const permute = (prefix, suffix, arr = []) => {
  if (suffix.length == 0) arr.push(prefix);
  else {
    for (let i = 0, len = suffix.length; i < len; i++) {
      permute(
        [...prefix, suffix[i]],
        [...suffix.slice(0, i), ...suffix.slice(i + 1)],
        arr
      );
    }
  }
  return arr;
};
console.log(permutation(["A", "B", "C"]));