Convert number to alphabet string (Javascript)

Question

I want to convert a number to a char like:

if number = 1 then A
if number = 26 then Z
if number = 27 then AA
if number = 676 then ZZ
if number = 456976 then ZZZZ

Tried to find anything to help me with but I did not had any lucky. Anybody have a sample for this using JavaScript?

Thank you!

This makes no sense. Is it only to be done with A and Z? Or were those just "corner case examples"? How would you get AB? DE? XYZ? — ishegg, Aug 20 '17 at 23:14
Where is the logic here ( 26 + 1 == AA ) && (26 * 26 == ZZ) ? — webdeb, Aug 20 '17 at 23:22

score 16 · Answer 1 · answered Aug 21 '17 at 04:20

The number conversion you've shown doesn't seem consistent. It seems you want to convert a number to the equivalent spreadsheet column letter, similar to this Python question: Convert spreadsheet number to column letter.

Converting that code to javascript (and cleaning up a bit) gives:

function numToSSColumn(num){
  var s = '', t;

  while (num > 0) {
    t = (num - 1) % 26;
    s = String.fromCharCode(65 + t) + s;
    num = (num - t)/26 | 0;
  }
  return s || undefined;
}


// A  Z AA  CZ  DA  YZ  ZZ AAA
[0,1,26,27,104,105,676,702,703,
//AAZ ABA  AZZ  BAA  BAZ  BBA   YYYZ   ZZZZ
  728,729,1378,1379,1404,1405,456976,475254].forEach(function(n) {
  console.log(n + ' : ' + numToSSColumn(n));
});

The function doesn't check the input and returns undefined if n < 0.

Your conversions don't seem to work because spreadsheet columns don't start from 0, they start from 1, so A-Z is 1 to 26, AA to AZ is 27 to 52, and so on. 676 is YZ and 456976 is YYYZ. ZZZZ is 475254 (or 11110 base26);

score 7 · Answer 2 · answered Aug 20 '17 at 22:55

7

You will need to write a loop, and mod (%) the number by 26 each time through and use the following:

 String.fromCharCode(num + 64) // if num is 1 then result is 'A'

answered Aug 20 '17 at 22:55

SlimSim

606
6
15

score 4 · Answer 3 · answered Jun 04 '20 at 15:20

I wrote a solution using recursion, well... just for fun really :)

const numberToBase26 = (val, tail = '') => {
  if (val <= 26) {
    return `${String.fromCharCode(val + 64)}${tail}`;
  }

  const remainder = val % 26 || 26;
  const division = Math.trunc(val / 26) - (remainder === 26 ? 1 : 0);

  return numberToBase26(division, `${String.fromCharCode(remainder + 64)}${tail}`);
};

console.log(numberToBase26(475254), ' should be equal to ZZZZ');

score 1 · Answer 4 · answered Aug 20 '17 at 23:16

You have very weird cases that are hard to understand. if 27 = AA, then 52 = ZZ but according to your example 676 = ZZ. Can you elaborate on the series that you want to generate. Just in case following is the algorithm that satisfies my example:

getAlphabetFromNumber = function (_num) {
    var str = "";

    multiples = Math.ceil(_num / 26);
    _charAtCode = _num - ((multiples - 1) * 26)

    for (let i = 0; i < multiples; i++)
        str += String.fromCharCode(_charAtCode + 64);

    return str;
}

score 1 · Answer 5 · answered Jun 12 '20 at 12:33

The important part is charCodeAt which returns the ASCII value for any character.

function columnIndex(name) {
    let index = 0;

    name = name.toUpperCase().split('');

    for (let i = name.length - 1; i >= 0; i--) {
        let piece = name[i];
        let colNumber = piece.charCodeAt() - 64;
        index = index + colNumber * Number(Math.pow(26, name.length - (i + 1)));
    }

    return index;
}

['A', 'AA', 'AAA', 'AAB', 'MMMM', 'MMMN'].forEach((n) => {
    console.log(n + ' : ' + columnIndex(n));
});

score 0 · Answer 6 · answered Aug 20 '17 at 23:01

Here's a start, open your inspector, select console. and paste this in:

cvt = function(n) {return(String.fromCharCode(n+'A'.charCodeAt(0)-1))}

Now you can type cvt(1) to get 'A', or cvt(26) to get 'Z'

It only works for one character. The rest is for you to work out

Convert number to alphabet string (Javascript)

6 Answers6