This is probably an unusual request, but for my script I need a function that increments by letter instead of number. For example:
This is a numeric example:
var i = 0;
while(condition){
window.write('We are at '+i);
++i;
}
Essentially, I want to count with letters, like Microsoft Excel does, instead of numbers. So instead of printing "We are at 0", "We are at 1", "We are at 2", etc., I need to print "We are at A", "We are at B", "We are at C", etc.
To mimic Excel (the only example I can think of), after reaching index 25 (Z), we could move on to 'AA', 'AB', 'AC', etc.
So it would work great like so:
var i = 0;
while(condition){
window.write('We are at '+toLetter(i));
++i;
}
Even better if somebody can write a function that then converts a letter back into a digit, i.e. toNumber('A') = 0 or toNumber('DC') = 107 (I think).
Thanks!
This is probably an unusual request, but for my script I need a function that increments by letter instead of number. For example:
This is a numeric example:
var i = 0;
while(condition){
window.write('We are at '+i);
++i;
}
Essentially, I want to count with letters, like Microsoft Excel does, instead of numbers. So instead of printing "We are at 0", "We are at 1", "We are at 2", etc., I need to print "We are at A", "We are at B", "We are at C", etc.
To mimic Excel (the only example I can think of), after reaching index 25 (Z), we could move on to 'AA', 'AB', 'AC', etc.
So it would work great like so:
var i = 0;
while(condition){
window.write('We are at '+toLetter(i));
++i;
}
Even better if somebody can write a function that then converts a letter back into a digit, i.e. toNumber('A') = 0 or toNumber('DC') = 107 (I think).
Thanks!
Here's a simple recursive function to convert the numbers to letters.
It's one-based, so 1 is A, 26 is Z, 27 is AA.
function toLetters(num) {
"use strict";
var mod = num % 26,
pow = num / 26 | 0,
out = mod ? String.fromCharCode(64 + mod) : (--pow, 'Z');
return pow ? toLetters(pow) + out : out;
}
Here's a matching function to convert the strings back to numbers:
function fromLetters(str) {
"use strict";
var out = 0, len = str.length, pos = len;
while (--pos > -1) {
out += (str.charCodeAt(pos) - 64) * Math.pow(26, len - 1 - pos);
}
return out;
}
A test: http://jsfiddle.net/St6c9/
Something like this you mean?
function num2chars(num, upper){
num2chars.letters = num2chars.letters || 'abcdefghijklmnopqrstuvwxyz'.split('');
var ret = repeat(num2chars.letters[num%26],Math.floor(num/26));
function repeat(chr,n){
if (n<1) {return chr;}
return new Array(n+1).join(chr);
}
return upper ? ret.toUpperCase() : ret;
}
//usage
while(i<104){
console.log(num2chars((i+=1),true));
}
//=> A..Z, AA..ZZ, AAA..ZZZ
For future readers I leave what I think is a more straightforward solution:
const aLetterCode = 97
const getLetterFromId = (number) => String.fromCharCode(aLetterCode + number)
console.log('code 0 ->', getLetterFromId(0)) // a
console.log('code 1 ->', getLetterFromId(1)) // b
console.log('code 12 ->', getLetterFromId(12)) // mCreate an array of letters A, B, C, D, etc. then call A by using array[0] since 0 is the index of A you can use array[i] as the index, just validate so i can't be over 25.
Use either of these ways to create the array:
var alphabet = new Array("A","B","C");
var alphabet = new Array(25);
alphabet[0] = "A";
alphabet[1] = "B";
alphabet[2] = "C";
instead of toLetter(i); use alphabet[i];
Try the following. Tried and tested in few minutes
var prefix = Array('','A','B'); //this will extends to 3x26 letters. Determines the Max generated
//first element of prefix is `''` so you can have A B C D
var prefix = Array('','A','B');
var alphabets = Array('A','B','C','D'); //extend this to Z
var letters = Array();
function fillArray()
{
var prefix_len = prefix.length;
var array_len = prefix_len * alphabets.length;
var alpha_len = alphabets.length;
for(var i=0; i<prefix_len; i++)
{
for(var a=0; a<alpha_len; a++)
letters.push(''+prefix[i]+alphabets[a]);
}
}
function getLetter(index)
{
return letters[index];
}
function generateTestValues()
{
fillArray();
//make sure 10 is less than letters.length
for(var i=0; i<10; i++)
document.write(getLetter(i)+' '); //A B C D AA AB AC AD BA BB BC....
}
HTML
<span id="clickable" onclick="generateTestValues()">Click Me</span>
Thats how you can generate random letters:
function getRandomArbitrary(min, max) {
max = Math.ceil(max);
min = Math.floor(min);
return Math.round(Math.random() * (max - min) + min);
}
function assignLetter(){
var group = ['A', 'B', 'C', 'D'];
var text = 'We are at ';
var str = '';
str = text + group[getRandomArbitrary(0, group.length-1)];
return str;
}
assignLetter();
Try the following:
function getCharCode(value) {
if (value===null || value === undefined) return "";
if (value < 26) return String.fromCharCode(65 + value);
return (
getCharCode(Number(value / 26) - 1) + String.fromCharCode(65 + (value % 26))
);
}