JavaScript: Generate all permutations of a string

JavaScript fundamental (ES6 Syntax): Exercise-136 with Solution

Write a JavaScript program to generate 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.
• Use Array.prototype.reduce() to combine all permutations in one array.
• Base cases are for String.prototype.length equal to 2 or 1.
• WARNING: The execution time increases exponentially with each character. Anything more than 8 to 10 characters will cause your environment to hang as it tries to solve all the different combinations.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2

// Define the 'stringPermutations' function.
const stringPermutations = str => {
  // Base case: If the length of the string is less than or equal to 2, return permutations accordingly.
  if (str.length <= 2) {
    return str.length === 2 ? [str, str[1] + str[0]] : [str];
  }

  // For longer strings, recursively generate permutations.
  return str.split('').reduce((acc, letter, i) => {
    const remainingChars = str.slice(0, i) + str.slice(i + 1); // Remove the current letter from the string.
    const permutations = stringPermutations(remainingChars); // Recursively generate permutations for the remaining characters.
    // For each permutation, concatenate the current letter and add it to the accumulator.
    return acc.concat(permutations.map(val => letter + val));
  }, []);
};

// Test the 'stringPermutations' function with different strings.
console.log(stringPermutations('abc'));  
console.log(stringPermutations('*$*'));

Output:

["abc","acb","bac","bca","cab","cba"]
["*$*","**$","$**","$**","**$","*$*"]

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-136-1 by w3resource (@w3resource) on CodePen.

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