A simple algorithm to find value from sequence for a Random number?

Question

I would like to create a general algorithm for the sequence (I am not storing the sequence anywhere).. if

1=A

2=B

3=C

.

.

.

26=Z

27=AA

28=AB

29=AC

30=AD

What should be the code to get the value of any random number ? e.g 333

Answer 1

A brilliant example here HERE ..

function getCharCode(displayNumber){
    var ordA = 'A'.charCodeAt(0);
    var ordZ = 'Z'.charCodeAt(0);
    var len = ordZ - ordA + 1;

    var returnSequence = "";
    while(displayNumber >= 0) {
        returnSequence = String.fromCharCode(displayNumber % len + ordA) + returnSequence; // (displayNumber % 26 + 65) +""
        displayNumber = Math.floor(displayNumber / len) - 1; //(displayNumber / 26) - 1
    }
    return returnSequence;
}

OR I modified this to ..

function getCharCode(displayNumber){
    var returnSequence = "";
    while(displayNumber >= 0) {
        returnSequence = String.fromCharCode(displayNumber % 26 + 65) + returnSequence;
        displayNumber = Math.floor(displayNumber / 26) - 1;
    }
    return returnSequence;
}

Answer 2

Try

var arr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("")
, i = -1
, n = -1
, len = 0
, max = arr.length + arr.length * arr.length
, res = {};

do {
  if (n === arr.length -1) {
    n = -1;
    ++i;
  };
  if (len < arr.length * 2 - 1) {
    res[++len] = len < arr.length + 1 ? arr[++n] : res[1] + arr[++n];
  } else {
    res[++len] = arr[i] + arr[++n]
  };
} while (len < max);

console.log("333:" + res[333], res);