Creating all possible unique permutations of a string in JavaScript

Problem

We are required to write a JavaScript function that takes in a string str. Our function should create all permutations of the input string and remove duplicates, if present. This means, we have to shuffle all letters from the input in all possible orders.

Example

Following is the code −

const str = 'aabb';
const permute = (str = '') => {
   if (!!str.length && str.length < 2 ){
      return str
   }
   const arr = [];
   for (let i = 0; i < str.length; i++){
      let char = str[i]
      if (str.indexOf(char) != i)
         continue
         let remainder = str.slice(0, i) + str.slice(i + 1, str.length)
         for (let permutation of permute(remainder)){
            arr.push(char + permutation)
         }
   }
   return arr
}
console.log(permute(str));

Output

Following is the console output −

[ 'aabb', 'abab', 'abba', 'baab', 'baba', 'bbaa' ]