Intermediate Exercism • typescript

Isbn Verifier

Challenge Overview

The ISBN-10 verification process is used to validate book identification numbers.

Source: Exercism typescript/isbn-verifier

💡 View Solution

export function isValid(isbn: string): boolean {
  const clean = isbn.replace(/-/g, '');
  if (clean.length !== 10) return false;
  
  let sum = 0;
  for (let i = 0; i < 10; i++) {
    const char = clean[i];
    let val: number;
    if (i === 9 && char === 'X') {
      val = 10;
    } else if (/[0-9]/.test(char)) {
      val = parseInt(char);
    } else {
      return false;
    }
    sum += val * (10 - i);
  }
  
  return sum % 11 === 0;
}