A string permutation example written in JavaScript (ES6)

StringPermutation.js

// NOTE: This is written using ES6 - make sure your JavaScript compiler is ES6 compliant


class StringPermutation {
	constructor(str) {
		this.originalString = str.slice(); // deep copy string
	}
	
	printAllPermutationsWithDuplicates() {
		this.permutate(
			this.originalString.split('').fill(1), // make string an array and set values to 1: [1,1,1,1]
			this.originalString, // "AABC"
			new Array(this.originalString.length).fill(0) // create blank array the size of the string with default defaulting to 0: [0,0,0,0]
		);
	}
	
	printAllPermutationsRemoveDuplicates() {
		let map = new Map();
		for (let ch of this.originalString) {
			map.set(ch, map.get(ch) === undefined ? 1 : map.get(ch) + 1);
		}
		this.permutate(
		  [...map.values()], // create an array from the values of the map: [2, 1, 1]
		  [...map.keys()], // create an array from the keys of the map: ['A', 'B', 'C']
		  new Array(this.originalString.length).fill(0) // create blank array the size of the string with default defaulting to 0: [0,0,0,0]
		);
	}
	
	permutate(setCount, keyMap, result = [], depth = 0) {
		if (depth == result.length) {
			console.log(result);
			return;
		}
		
		for (let i = 0; i < setCount.length; i++) {
			if (setCount[i] > 0) {
				result[depth] = keyMap[i];
				setCount[i]--;
				this.permutate(setCount, keyMap, result, depth + 1);
				setCount[i]++;
			}
		}
	}
}

let stringPermutation = new StringPermutation('AABC');

console.log(`
PRINTING ALL PERMUTATIONS WITH DUPLICATES SHOWING
=================================================`);
stringPermutation.printAllPermutationsWithDuplicates();



console.log(`\n
PRINTING ALL PERMUTATIONS WITH DUPLICATES REMOVED
=================================================`);
stringPermutation.printAllPermutationsRemoveDuplicates();




/// OUTPUT
//
// PRINTING ALL PERMUTATIONS WITH DUPLICATES SHOWING
// =================================================
// [ 'A', 'A', 'B', 'C' ]
// [ 'A', 'A', 'C', 'B' ]
// [ 'A', 'B', 'A', 'C' ]
// [ 'A', 'B', 'C', 'A' ]
// [ 'A', 'C', 'A', 'B' ]
// [ 'A', 'C', 'B', 'A' ]
// [ 'A', 'A', 'B', 'C' ]
// [ 'A', 'A', 'C', 'B' ]
// [ 'A', 'B', 'A', 'C' ]
// [ 'A', 'B', 'C', 'A' ]
// [ 'A', 'C', 'A', 'B' ]
// [ 'A', 'C', 'B', 'A' ]
// [ 'B', 'A', 'A', 'C' ]
// [ 'B', 'A', 'C', 'A' ]
// [ 'B', 'A', 'A', 'C' ]
// [ 'B', 'A', 'C', 'A' ]
// [ 'B', 'C', 'A', 'A' ]
// [ 'B', 'C', 'A', 'A' ]
// [ 'C', 'A', 'A', 'B' ]
// [ 'C', 'A', 'B', 'A' ]
// [ 'C', 'A', 'A', 'B' ]
// [ 'C', 'A', 'B', 'A' ]
// [ 'C', 'B', 'A', 'A' ]
// [ 'C', 'B', 'A', 'A' ]
//
//
// PRINTING ALL PERMUTATIONS WITH DUPLICATES REMOVED
// =================================================
// [ 'A', 'A', 'B', 'C' ]
// [ 'A', 'A', 'C', 'B' ]
// [ 'A', 'B', 'A', 'C' ]
// [ 'A', 'B', 'C', 'A' ]
// [ 'A', 'C', 'A', 'B' ]
// [ 'A', 'C', 'B', 'A' ]
// [ 'B', 'A', 'A', 'C' ]
// [ 'B', 'A', 'C', 'A' ]
// [ 'B', 'C', 'A', 'A' ]
// [ 'C', 'A', 'A', 'B' ]
// [ 'C', 'A', 'B', 'A' ]
// [ 'C', 'B', 'A', 'A' ]