wordPermutation.js

Make a permutation with a word or an array of letter. (e.g : 'no' have 2 possibilites of permutation, 'no' OR 'on').

How it works ?

This is based on Heap's algorithm. (I invite you to check wikipedia's page about it : https://en.wikipedia.org/wiki/Heap%27s_algorithm )

We have 3 function:

• heap() : Heap's algorithm
• wordSplitter() : Split word if array is a word (e.g ['hello']), because it's also can be an array of letters (e.g ['h','e','l','l','o'])
• Main function named permute() which call heap() and wordSplitter(). It take each letter of the heap returned array (called heapArr) and make a new posibilities. At the end, we have all posibilities into 'permutedArr' If the array 'myArray' contain a word, we call wordSplitter() to split the word into an array with letters. heap() need an array with letter to do his work !

Possibilities

We'll not using factorial in this code, but it's cool to know how many possibilities there's without calculating all existing combination.

There existing n! possibilities, which is equivalent to 1 * 2 * 3 * . . . * ( n - 1 ) * n. Clearly, with a word of 4 letters, we will have 24 possibilities, because: 4! = 4 * 3 * 2 * 1 = 24

Pretty astonishing when you see a word with 5 letters have 120 combination possible. I let you imagine a word with much more letters...

(Fun Fact ? : Your words possibilities will start with the same letter (or number) (n-1)! times. But it's only a conjecture from me, not verified !)

Improvement ?

Any advice to improve the code ? Pull a request, it can only be more cool !