Generates all permutations of a string

stringPermutations.js

function stringPermutations (str) {
  if (str.length <=2) {
    return str.length === 2 ? [str, str[1] + str[0]] : [str];
  }

  return [...str].reduce((acc, letter, i) => {
      const letters = str.slice(0, i) + str.slice(i + 1);
      const transformString = stringPermutations(letters).map(item => letter + item);
      return [...acc, ...transformString];
    }, []);
  
}

stringPermutations('abc'); // ['abc', 'acb', 'bac', 'bca', 'cab', 'cba']