javascript check alphabet code example

Example 1: javascript number in alphabet

// converts numbers to spreadsheet letter columns eg. 1 -> A
function numToSSColumn(num){
  let s = '', t;

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

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

Example 2: checking if a character is an alphabet in js

function isLetter(str) {
  return str.length === 1 && str.match(/[a-z]/i);
}

Example 3: how to check if a string is alphabetic in javascript

function isAlphaOrParen(str) {
  return /^[a-zA-Z()]+$/.test(str);
}

/*/^[a-zA-Z()]*$/ - also returns true for an empty string
/^[a-zA-Z()]$/ - only returns true for single characters.
/^[a-zA-Z() ]+$/ - also allows spaces*/
//better regEX to include question marks too

Example 4: check for alphabetic string in javascript

function isAlphaOrParen(str) {
  return /^[a-zA-Z()]+$/.test(str);
}