Best way to alphanumeric check in JavaScript

Question

What is the best way to perform an alphanumeric check on an INPUT field in JSP? I have attached my current code

Answer 1

If you want a simplest one-liner solution, then go for the accepted answer that uses regex.

However, if you want a faster solution then here's a function you can have.

console.log(isAlphaNumeric('a')); // true
console.log(isAlphaNumericString('HelloWorld96')); // true
console.log(isAlphaNumericString('Hello World!')); // false

/**
 * Function to check if a character is alpha-numeric.
 *
 * @param {string} c
 * @return {boolean}
 */
function isAlphaNumeric(c) {
  const CHAR_CODE_A = 65;
  const CHAR_CODE_Z = 90;
  const CHAR_CODE_AS = 97;
  const CHAR_CODE_ZS = 122;
  const CHAR_CODE_0 = 48;
  const CHAR_CODE_9 = 57;

  let code = c.charCodeAt(0);

  if (
    (code >= CHAR_CODE_A && code <= CHAR_CODE_Z) ||
    (code >= CHAR_CODE_AS && code <= CHAR_CODE_ZS) ||
    (code >= CHAR_CODE_0 && code <= CHAR_CODE_9)
  ) {
    return true;
  }

  return false;
}

/**
 * Function to check if a string is fully alpha-numeric.
 *
 * @param {string} s
 * @returns {boolean}
 */
function isAlphaNumericString(s) {
  for (let i = 0; i < s.length; i++) {
    if (!isAlphaNumeric(s[i])) {
      return false;
    }
  }

  return true;
}