Convert integer into its character equivalent, where 0 => a, 1 => b, etc

Convert integer into its character equivalent, where 0 => a, 1 => b, etc

I want to convert an integer into its character equivalent based on the alphabet. For example:
0 => a
1 => b
2 => c
3 => d

etc. I could build an array and just look it up when I need it but I’m wondering if there’s a built in function to do this for me. All the examples I’ve found via Google are working with ASCII values and not a character’s position in the alphabet.


Solution 1:

Assuming you want lower case letters:

var chr = String.fromCharCode(97 + n); // where n is 0, 1, 2 ...

97 is the ASCII code for lower case ‘a’. If you want uppercase letters, replace 97 with 65 (uppercase ‘A’). Note that if n > 25, you will get out of the range of letters.

Solution 2:

Will be more portable in case of extending to other alphabets:


or, to be more compatible (with our beloved IE):


Solution 3:

If you don’t mind getting multi-character strings back, you can support arbitrary positive indices:

function idOf(i) {
    return (i >= 26 ? idOf((i / 26 >> 0) - 1) : '') +  'abcdefghijklmnopqrstuvwxyz'[i % 26 >> 0];

idOf(0) // a
idOf(1) // b
idOf(25) // z
idOf(26) // aa
idOf(27) // ab
idOf(701) // zz
idOf(702) // aaa
idOf(703) // aab

(Not thoroughly tested for precision errors 🙂

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Solution 4:

A simple answer would be (26 characters):


If space is precious you could do the following (20 characters):


Think about what you could do with all those extra bytes!

How this works is you convert the number to base 36, so you have the following characters:

^         ^
n        n+10

By offsetting by 10 the characters start at a instead of .

Not entirely sure about how fast running the two different examples client-side would compare though.

Solution 5:

Javascript’s String.fromCharCode(code1, code2, …, codeN) takes an infinite number of arguments and returns a string of letters whose corresponding ASCII values are code1, code2, … codeN. Since 97 is ‘a’ in ASCII, we can adjust for your indexing by adding 97 to your index.

function indexToChar(i) {
  return String.fromCharCode(i+97); //97 in ASCII is 'a', so i=0 returns 'a', 
                                    // i=1 returns 'b', etc

Solution 6:

Use String.fromCharCode. This returns a string from a Unicode value, which matches the first 128 characters of ASCII.

var a = String.fromCharCode(97);