Beginner Exercism • javascript

Isbn Verifier

Challenge Overview

The [ISBN-10 verification process][isbn-verification] is used to validate book identification numbers. These normally contain dashes and look like: `3-598-21508-8`

Source: Exercism javascript/isbn-verifier

💡 View Solution

export const isValid = (isbn) => {
  const clean = isbn.replace(/-/g, '');
  if (!/^\d{9}[\dX]$/.test(clean)) return false;

  const sum = [...clean].reduce((acc, char, index) => {
    const value = char === 'X' ? 10 : Number(char);
    return acc + value * (10 - index);
  }, 0);

  return sum % 11 === 0;
};