cdigit
Version:
Collection of check digit algorithms implemented in JavaScript
61 lines (60 loc) • 1.81 kB
JavaScript
/**
* cdigit
*
* @copyright 2018-2023 LiosK
* @license (MIT OR Apache-2.0)
*/
class GTIN {
constructor(name, longName) {
this.name = name;
this.longName = longName;
}
computeFromNumVals(ns) {
if (ns.length === 0) {
throw new SyntaxError("string to be protected is empty");
}
else if (ns.some((e) => e < 0 || e > 9 || !Number.isInteger(e))) {
throw new SyntaxError("invalid numerical value detected");
}
let sum = 0;
let odd = 1;
for (let i = ns.length - 1; i >= 0; i -= 1) {
if (sum > 281474976710655) {
// ~2^48 at max
sum %= 10;
}
sum += ns[i] * (odd ? 3 : 1);
odd ^= 1;
}
return [(10 - (sum % 10)) % 10];
}
compute(s) {
const ds = String(s).replace(/[^0-9]/g, "");
const ns = [...ds].map(Number);
return String(this.computeFromNumVals(ns)[0]);
}
parse(s) {
const m = String(s).match(/^(.*)([0-9])$/s);
if (m != null) {
return [m[1], m[2]];
}
else {
throw new SyntaxError("could not find check character(s)");
}
}
generate(s) {
return `${s}${this.compute(s)}`;
}
validate(s) {
const [bare, cc] = this.parse(s);
return this.compute(bare) === cc;
}
}
/**
* The standard check digit algorithm for GS1 data structures (including GTIN).
*
* Note: This implementation does not check the length of a number; however, it
* is not recommended to use numbers longer than 18 digits because GS1 General
* Specifications do not explicitly specify an algorithm for them.
*/
export const gtin = new GTIN("gtin", "GTINs (including UPC, EAN, ISBN-13, etc.)");