---
title: stringPermutations
tags: string,recursion,advanced
---

Generates all permutations of a string (contains duplicates).

⚠️ **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.

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']
```