### stringPermutations

⚠️ **WARNING**: This function's execution time increases exponentially with each character. Anything more than 8 to 10 characters will cause your browser to hang as it tries to solve all the different combinations.

Generates all permutations of a string (contains duplicates).

Use recursion.
For each letter in the given string, create all the partial permutations for the rest of its letters.
Use `Array.prototype.map()` to combine the letter with each partial permutation, then `Array.prototype.reduce()` to combine all permutations in one array.
Base cases are for string `length` equal to `2` or `1`.

```js
const stringPermutations = str => {
  if (str.length <= 2) return str.length === 2 ? [str, str[1] + str[0]] : [str];
  return str
    .split('')
    .reduce(
      (acc, letter, i) =>
        acc.concat(stringPermutations(str.slice(0, i) + str.slice(i + 1)).map(val => letter + val)),
      []
    );
};
```

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