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/**
* The most commonly used EAN standard is
* the thirteen-digit EAN-13, while the
* less commonly used 8-digit EAN-8 barcode was
* introduced for use on small packages.
* EAN consists of:
* GS1 prefix, manufacturer code, product code and check digit
* Reference: https://en.wikipedia.org/wiki/International_Article_Number
*/
import assertString from './util/assertString';
/**
* Define EAN Lenghts; 8 for EAN-8; 13 for EAN-13
* and Regular Expression for valid EANs (EAN-8, EAN-13),
* with exact numberic matching of 8 or 13 digits [0-9]
*/
var LENGTH_EAN_8 = 8;
var validEanRegex = /^(\d{8}|\d{13})$/;
/**
* Get position weight given:
* EAN length and digit index/position
*
* @param {number} length
* @param {number} index
* @return {number}
*/
function getPositionWeightThroughLengthAndIndex(length, index) {
if (length === LENGTH_EAN_8) {
return index % 2 === 0 ? 3 : 1;
}
return index % 2 === 0 ? 1 : 3;
}
/**
* Calculate EAN Check Digit
* Reference: https://en.wikipedia.org/wiki/International_Article_Number#Calculation_of_checksum_digit
*
* @param {string} ean
* @return {number}
*/
function calculateCheckDigit(ean) {
var checksum = ean.slice(0, -1).split('').map(function (_char, index) {
return Number(_char) * getPositionWeightThroughLengthAndIndex(ean.length, index);
}).reduce(function (acc, partialSum) {
return acc + partialSum;
}, 0);
var remainder = 10 - checksum % 10;
return remainder < 10 ? remainder : 0;
}
/**
* Check if string is valid EAN:
* Matches EAN-8/EAN-13 regex
* Has valid check digit.
*
* @param {string} str
* @return {boolean}
*/
export default function isEAN(str) {
assertString(str);
var actualCheckDigit = Number(str.slice(-1));
return validEanRegex.test(str) && actualCheckDigit === calculateCheckDigit(str);
}
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