const strPermutations = str => {

if (str.length < 2) {

return str; // This is our break condition

}

let permutations = []; // This array will hold our permutations

for (let i = 0, len = str.length; i < len; i++) {

let char = str[i];

let remainingString = `${str.slice(0,i)}${str.slice(i+1)}`;

for (let subPermutation of strPermutations(remainingString)) {

permutations.push(char + subPermutation);

}

}

return permutations;

}

console.log(strPermutations("abcd"));

// ["abcd", "abdc", "acbd", "acdb", "adbc", "adcb", "bacd", "badc", "bcad", "bcda", "bdac", "bdca", "cabd",

// "cadb", "cbad", "cbda", "cdab", "cdba", "dabc", "dacb", "dbac", "dbca", "dcab", "dcba"]

// Permuation of an array

function permutation(input) {

let outputs = [[input[0]]];

for (let i = 1; i < input.length; i++) {

let current = [];

for (let j = 0; j < outputs.length; j++) {

let base = outputs[j];

for (let k = 0; k <= base.length; k++) {

let temp = base.slice();

temp.splice(k, 0, input[i]);

current.push(temp);

}

}

outputs = current;

}

return outputs;

}

console.log(permutation(["a", "b", "c", "d"]));

//[["d", "c", "b", "a"], ["c", "d", "b", "a"], ["c", "b", "d", "a"], ["c", "b", "a", "d"], ["d", "b", "c", "a"],

// ["b", "d", "c", "a"], ["b", "c", "d", "a"], ["b", "c", "a", "d"], ["d", "b", "a", "c"], ["b", "d", "a", "c"],

// ["b", "a", "d", "c"], ["b", "a", "c", "d"], ["d", "c", "a", "b"], ["c", "d", "a", "b"], ["c", "a", "d", "b"],

// ["c", "a", "b", "d"], ["d", "a", "c", "b"], ["a", "d", "c", "b"], ["a", "c", "d", "b"], ["a", "c", "b", "d"],

// ["d", "a", "b", "c"], ["a", "d", "b", "c"], ["a", "b", "d", "c"], ["a", "b", "c", "d"]]