Luhn validation of swedish personal id number

nic_validate_se_persnr_mod.js

/**
 * @NApiVersion 2.1
 *
 * @Description nic_validate_se_persnr_mod.js
 * @Solution Generic module
 *
 * @Copyright 2023 Noresca IT Consulting AB
 * @Author jorg.ramb <jorg.ramb@noresca.se>
 *
 * # Explanation
 * "It should be SSN" - no, the SSN is something used in the USA, it is not a good translation actually and Skatteverket uses a different term
 *
 * Below validation applies to several things at the same time. In Swedish:
 *   - Personnummer = Personal Identification Number
 *   - Organisationsnummer = Company Registration Number
 *   - Samordningsnummer = Co-ordination number
 *     - A co-ordination number is an identification for people who are not or have not been registered in Sweden.
 *       The purpose of co-ordination numbers is so that public agencies
 *       and other functions in society are able to identify people even if they are not registered in Sweden.
 *
 * So... f-it, I am writing "checkLuhn", because that guy deserves some credit.
 *
 * Sources:
 *  https://www.mira.se/knowledge-base/vad-heter-personnummer-och-samordningsnummer-pa-engelska/#:~:text=%E2%80%9CSocial%20security%20number%E2%80%9D%20%C3%A4r%20snarast,faktiskt%20menar%20ett%20svenskt%20personnummer.&text=A%20co%2Dordination%20number%20is,not%20been%20registered%20in%20Sweden.
 *  https://www.skatteverket.se/servicelankar/otherlanguages/inenglishengelska/individualsandemployees/livinginsweden/personalidentitynumbers.4.2cf1b5cd163796a5c8b4295.html
 */

define( [],
    () => {
        /**
         * Handles (formats/validates) a Swedish "Personnummer" (aka slightly missleading "SSN"). /jramb
         * @typedef {Object} PersnrParsedResult
         * @property {boolean} valid - valid both in format and checksum
         * @property {string} type -  ORG or PERSON (samordningsnumber also are PERSON!)
         * @property {boolean} samordningsnummer
         * @property {boolean} wellformed - format looks right (not necessarily valid)
         * @property {string[]} parts - list of parts of the personnummer
         *
         * @param {string} persnrStr - personal/coordination/company number as string
         * @return {PersnrParsedResult} - the parsed result
         */
        function checkLuhn(persnrStr) {
            if (typeof persnrStr !== "string") return {};
            const nrRE = /^(19|20)?([0-9]{2})([0-9]{2})([0-9]{2})(-|\+)?([0-9]{4})$/;
            let parts = persnrStr.match(nrRE);
            // parts: 0=all, 1= century/null, 2=year*(2 digit), 3=month*, 4=day*, 5=delimiter/null, 6=lastfour
            let wellformed = !!parts;
            if (!wellformed) {
                return { wellformed, valid: false };
            }
            parts[1] = parts[1] || ''; //convert null to empty string
            parts[5] = parts[5] || '';
            const cleaned = persnrStr.replace(/[+-]/g,''); // only light cleaning

            const luhnCheck = numStr => {
                const dub = [0, 2, 4, 6, 8, 1, 3, 5, 7, 9];
                let sum=0;
                let f = numStr.length%2===0;
                (numStr+'').split('').forEach(c => {
                    let val = parseInt(c);
                    sum += f?dub[val]:val;
                    f = !f;
                });
                return sum%10 === 0;
            }
            let century = parts[1]; // guessed century, if empty
            const centuryMissing = !century;
            if (centuryMissing) {
                // completely arbitrary: xx < cutoff => 20xx, xx > cutoff => 19xx
                const cutoff = 11;
                century = (parseInt(parts[2])<cutoff?'20':'19');
            }
            const type = parseInt(parts[3])>=20?'ORG':'PERSON';
            let extraPerson = {};
            if (type==='PERSON') {
                const samordningsnummer = parseInt(parts[4])>60;
                const dayAdd = 60;
                extraPerson = {
                    samordningsnummer,
                    birthdate: new Date(century + parts[2], parts[3] - 1, samordningsnummer ? (parts[4] - dayAdd) : parts[4]),
                    female: type==='PERSON' && parseInt(parts[6].substring(2,3))%2===0,
                }
            }
            return {
                parts, cleaned, century, centuryMissing, wellformed, type,
                cleaningNecessary: persnrStr !== cleaned,
                masked: parts[1]+parts[2]+'****'+(parts[5]?parts[5]:'-')+parts[6],
                formatted: century+parts[2]+parts[3]+parts[4]+(parts[5]?parts[5]:'-')+parts[6],
                valid : luhnCheck(parts[2]+parts[3]+parts[4]+parts[6]),
                ...extraPerson
            };
        }

        return { checkLuhn };
    }
)