This program computes all possible alphanumeric passwords of 

length three, using only very basic JS so that new programmers

can understand the code. 

​

However, with recent built-in JS functions, it's 

possible to compute the Cartesian product of arbitrarily 

many arrays in just one line of code. See 

​

https://stackoverflow.com/questions/12303989/cartesian-product-of-multiple-arrays-in-javascript

​

In the solution given there, n-tuples are represented as arrays

of length n, so it would need to be modified to return passwords

of length n as strings.

*/

​

let pass1; //array of 1-character passwords

let pass3; //array of 3-character passwords

​

pass1 = [

  'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 

  'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',

  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'

];

​

//returns Cartesian product of two arrays of strings

//arr1 = [x1, ... , xm] and arr2 = [y1, ..., yn],

//with the ordered pair (x,y) represented as 'xy'

​

function cartesian(arr1, arr2) {

  let product = [];

  for (let i = 0; i < arr1.length; i++) {

    for (let j = 0; j < arr2.length; j++) {

      product.push(arr1[i]+arr2[j]);

    }

  }

  return product;

}

​

pass3 = cartesian(cartesian(pass1, pass1), pass1);

​

//check we have 36 ** 3 = 46656 passwords

console.log(pass3.length);

​

//log a random password

let randomIndex = Math.floor(Math.random() * pass3.length);

console.log(pass3[randomIndex]);