查找JavaScript字符串的所有组合

Question

I just read an interesting article Bruce Schneier - Choosing Secure Passwords and came up with the idea of finding out how long it would take JavaScript to "crack" my own password (a string/ the function parameter).

How can I write a function, that simply compares all possible combinations of letters (and later numbers, maybe special characters etc.) with a certain input parameter (type is string) of that function. The possible characters will be listed in an array.

eg:

var letterDB = ["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", "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"];
// actually I would like to use a Regular Expression instead of my own letterDB, but for the beginning it is fine.

I could find a solution for input parameters of only 1 letter (but I am still missing to pass longer strings into that function). It is very confusing how to handle the problem of strings like "cloud", "play", etc. I am thinking about solving this issue with a for-loop but I don't really know where to start with the loop and how I programm loops for inputs that I dont' know the length yet.

My function:

function crack(x) {
  var timerStart = Date.now();  //for curiosity I want to log the time of the entire calculation
  var s = String(x);            //make sure the input is of type string (gets interesting when numbers are used in the string)

  for(i=0; i < letterDB.length; i++) {
      if (s == letterDB[i]) {
          console.log("found same combination as your input");
          console.log("letter was: " + letterDB[i]);
          console.log("interval: " + i);
          console.log("calculation time:", Date.now() - timerStart);  //interesting to see the time of the calculation when my input parameters will get longer and harder to crack because of special characters.
      }
  }
}

Answer 1

You can simply loop through the string and iterate over all the letters:

function crack(x) {
    var timerStart = Date.now();
    x = x.toString();
    var charsArr = s.split('');
    var result = charsArr.every(function(char) {
        return letterDB.includes(char);
    });
    if (result) {
        console.log("Success! calculation time:", Date.now() - timerStart);
    }
    console.log("fail");
    return result;
}

If result is true, then it means that you can build the string from the letterDB array.

Answer 2

As said in the comments, this will take forever. However, it's relatively simple to implement a permutation-based cracker with recursion.

var input = "ad";
var done = false;
var maxLength = 2;
var letterDB = ["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", "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"];

function recursion (str) {
   for (var i=0; i < letterDB.length; i++) {
      var test = str+letterDB[i];
      if (test !== input && !done && str.length < maxLength) {
         recursion(test);
      } else if (test === input) {
         done = true;
         alert("your pass is "+test);
      }
   }
}
recursion("");

To gauge how slow this is, the password cloud took me 33 seconds to find (with maxlength correctly set). The time would escalate extremely quickly for anything with a larger length.