JAVASCRIPT

javascript alphabet to number

/**
 * Converts a spreadsheet column letter to a number. eg. A -> 1
 * 
 * @param {String} str - (required) The spreadsheet column letter to convert to a number.
 * 
 * @returns {(Number|undefined)} The column number or undefined.
 */
function convertLetterToNumber(str) {
  if ((typeof str === "string" || str instanceof String) && /^[a-zA-Z]+$/.test(str)) {
    str = str.toUpperCase();
    let out = 0,
      len = str.length;
    for (pos = 0; pos < len; pos++) {
      out += (str.charCodeAt(pos) - 64) * Math.pow(26, len - pos - 1);
    }
    return out;
  } else {
    return undefined;
  }
}

convertLetterToNumber("A"); // 1
convertLetterToNumber("b"); // 2
convertLetterToNumber("Ba"); // 53
convertLetterToNumber("dE"); // 109
convertLetterToNumber("ZZZZ"); // 475254

convertLetterToNumber("A"); // 1
convertLetterToNumber("b"); // 2
convertLetterToNumber("Ba"); // 53
convertLetterToNumber("dE"); // 109
convertLetterToNumber("ZZZZ"); // 475254

alphabet to number javascript

str = 'z'
n = (str == str.toLowerCase()) ? 96 : 64
result = str.charCodeAt(0) - n
console.log(result);

javascript number in alphabet

/**
 * Convert a whole number that is more than zero to a spreadsheet column letters. eg. 1 -> A
 * Source: https://stackoverflow.com/questions/45787459/convert-number-to-alphabet-string-javascript/45787487
 * 
 * @param {Number} num - (required) The number to convert to a spreadsheet column letter. Must be greater than zero.
 *
 * @returns {(String|undefined)} The spreadsheet column letter or undefined.
 */
function numToSSColumnLetter(num) {
  let columnLetter = "",
    t;

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

numToSSColumn(0); // undefined
numToSSColumn(1); // A
numToSSColumn(26); // Z
numToSSColumn(-1); // undefined
numToSSColumn(27); // AA
numToSSColumn(475254); // ZZZZ