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

Removed NOT operation in alpha-numeric validation. Moved variables to block level scope. Some comments here and there. Derived from the best Micheal

function isAlphaNumeric ( str ) {

  /* Iterating character by character to get ASCII code for each character */
  for ( let i = 0, len = str.length, code = 0; i < len; ++i ) {

    /* Collecting charCode from i index value in a string */
    code = str.charCodeAt( i ); 

    /* Validating charCode falls into anyone category */
    if (
        ( code > 47 && code < 58) // numeric (0-9)
        || ( code > 64 && code < 91) // upper alpha (A-Z)
        || ( code > 96 && code < 123 ) // lower alpha (a-z)
    ) {
      continue;
    } 

    /* If nothing satisfies then returning false */
    return false
  }

  /* After validating all the characters and we returning success message*/
  return true;
};

console.log(isAlphaNumeric("oye"));
console.log(isAlphaNumeric("oye123"));
console.log(isAlphaNumeric("oye%123"));