traceprompt-node/src/piiDetector/utils/luhn.ts

Client-side encrypted, audit-ready logging for LLM applications

export function luhnValid(num: string): boolean {
  const digits = num.replace(/\D+/g, "").split("").map(Number).reverse();
  let sum = 0;
  for (let i = 0; i < digits.length; i++) {
    let n = digits[i];
    if (i % 2 === 1) {
      n *= 2;
      if (n > 9) n -= 9;
    }
    sum += n;
  }
  return sum % 10 === 0;
}