[barcode] #barcode #gtin #ean

isGTIN.js

/**
 * Check if code is EAN13
 *
 * @link https://github.com/hampus-nilsson/gs1-checkdigit/blob/main/checkdigit.js
 * @param {string} input
 * @returns {boolean}
 */
export function isGTIN(input) {
  if (![8, 12, 13, 14].includes(input.length)) return false;

  const digs = input.split("").reverse();

  let total = 0;

  for (let i = 1; i < digs.length; i++) {
    const num = parseInt(
      // @ts-expect-error skip
      digs[i]
    );

    if (Number.isNaN(num)) return false;

    if (i % 2 === 0) {
      total += num;
    } else {
      total += num * 3;
    }
  }

  const check = Math.ceil(total / 10) * 10 - total;

  // @ts-expect-error skip
  return parseInt(digs[0]) === check;
}