72 lines
2.1 KiB
JavaScript
72 lines
2.1 KiB
JavaScript
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/**
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* The most commonly used EAN standard is
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* the thirteen-digit EAN-13, while the
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* less commonly used 8-digit EAN-8 barcode was
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* introduced for use on small packages.
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* Also EAN/UCC-14 is used for Grouping of individual
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* trade items above unit level(Intermediate, Carton or Pallet).
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* For more info about EAN-14 checkout: https://www.gtin.info/itf-14-barcodes/
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* EAN consists of:
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* GS1 prefix, manufacturer code, product code and check digit
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* Reference: https://en.wikipedia.org/wiki/International_Article_Number
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* Reference: https://www.gtin.info/
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*/
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import assertString from './util/assertString';
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/**
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* Define EAN Lenghts; 8 for EAN-8; 13 for EAN-13; 14 for EAN-14
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* and Regular Expression for valid EANs (EAN-8, EAN-13, EAN-14),
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* with exact numberic matching of 8 or 13 or 14 digits [0-9]
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*/
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var LENGTH_EAN_8 = 8;
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var LENGTH_EAN_14 = 14;
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var validEanRegex = /^(\d{8}|\d{13}|\d{14})$/;
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/**
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* Get position weight given:
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* EAN length and digit index/position
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*
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* @param {number} length
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* @param {number} index
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* @return {number}
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*/
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function getPositionWeightThroughLengthAndIndex(length, index) {
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if (length === LENGTH_EAN_8 || length === LENGTH_EAN_14) {
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return index % 2 === 0 ? 3 : 1;
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}
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return index % 2 === 0 ? 1 : 3;
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}
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/**
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* Calculate EAN Check Digit
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* Reference: https://en.wikipedia.org/wiki/International_Article_Number#Calculation_of_checksum_digit
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*
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* @param {string} ean
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* @return {number}
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*/
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function calculateCheckDigit(ean) {
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var checksum = ean.slice(0, -1).split('').map(function (_char, index) {
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return Number(_char) * getPositionWeightThroughLengthAndIndex(ean.length, index);
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}).reduce(function (acc, partialSum) {
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return acc + partialSum;
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}, 0);
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var remainder = 10 - checksum % 10;
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return remainder < 10 ? remainder : 0;
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}
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/**
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* Check if string is valid EAN:
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* Matches EAN-8/EAN-13/EAN-14 regex
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* Has valid check digit.
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*
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* @param {string} str
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* @return {boolean}
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*/
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export default function isEAN(str) {
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assertString(str);
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var actualCheckDigit = Number(str.slice(-1));
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return validEanRegex.test(str) && actualCheckDigit === calculateCheckDigit(str);
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}
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