CODEWITHSUNDEEP
javascriptdata-conversion
Ricardo Andrade
Ricardo Andrade

Reputation: 137

Convert number to alphabet string (Javascript)

I want to convert a number to a char like:

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!

Upvotes: 11

Views: 24702

Answers (6)

Navanshu Rastogi
Navanshu Rastogi

Reputation: 43

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));
});

Upvotes: 1

codeKonami
codeKonami

Reputation: 960

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');

Upvotes: 4

RobG
RobG

Reputation: 147363

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);

Upvotes: 16

imixtron
imixtron

Reputation: 303

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;
}

Upvotes: 1

Mikkel
Mikkel

Reputation: 7777

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

Upvotes: 0

SlimSim
SlimSim

Reputation: 616

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'

Upvotes: 8

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