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

In a tight loop, it's probably better to avoid regex and hardcode your characters:

const CHARS = new Set("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
function isAlphanumeric(char) {
    return CHARS.has(char);
}