National identity number validator

.changeset/shy-heads-cross.md

@@ -0,0 +1,18 @@
+---
+"@obosbbl/validation": minor
+---
+
+add method `validateNationalIdentityNumber()`
+
+Validates that the input is a valid Norwegian national identity number (either a fødselsnummer or a D-nummer).
+It validates the checksum and checks if the date of birth is valid.
+
+```
+import { validateNationalIdentityNumber } from "@obosbbl/validation/no";
+
+// Fødselsnummer
+validatePersonalIdentityNumber('21075417753') // => true
+
+// D-nummer
+validatePersonalIdentityNumber('53097248016') // => true
+```

packages/validation/README.md

@@ -57,6 +57,7 @@ validateOrganizationNumber('937 052 766', { allowFormatting: true }) // true;
 
 ## Methods
 
+* validateNationalIdentityNumber
 * validatePostalCode
 * validatePhoneNumber
   * supports mobileOnly option

packages/validation/package.json

@@ -29,5 +29,8 @@
   ],
   "scripts": {
     "build": "bunchee"
+  },
+  "devDependencies": {
+    "nav-faker": "3.2.4"
   }
 }

packages/validation/src/no.ts

@@ -103,3 +103,66 @@ export function validateObosMembershipNumber(
 
   return /^\d{7}$/.test(value);
 }
+
+type PersonalIdentityNumberOptions = ValidatorOptions;
+
+/**
+ * Validates that the input value is a Norwegian national identity number (fødselsnummer or d-nummer).
+ *
+ * It validates the control digits and checks if the date of birth is valid.
+ *
+ * @example
+ * ```
+ * // Fødselsnummer
+ * validatePersonalIdentityNumber('21075417753') // => true
+ *
+ * // D-nummer
+ * validatePersonalIdentityNumber('53097248016') // => true
+ * ```
+ */
+export function validateNationalIdentityNumber(
+  value: string,
+  options: PersonalIdentityNumberOptions = {},
+): boolean {
+  if (options.allowFormatting) {
+    // biome-ignore lint/style/noParameterAssign:
+    value = stripFormatting(value);
+  }
+
+  // Norwegian national identity numbers use mod 11 with two control digits.
+  // The first one is calculated for the first 10d digits
+  // while the last one uses all 11 digits
+  const valueForControlDigit1 = value.slice(0, -1);
+  const controlDigit1 = mod11(
+    valueForControlDigit1,
+    [3, 7, 6, 1, 8, 9, 4, 5, 2],
+  );
+
+  const controlDigit2 = mod11(value, [5, 4, 3, 2, 7, 6, 5, 4, 3, 2]);
+
+  if (!controlDigit1 || !controlDigit2) {
+    return false;
+  }
+
+  // copy/inspiration from NAV https://github.com/navikt/fnrvalidator/blob/77e57f0bc8e3570ddc2f0a94558c58d0f7259fe0/src/validator.ts#L108
+  let day = Number(value.substring(0, 2));
+  const month = Number(value.substring(2, 4));
+  let year = Number(value.substring(4, 6));
+
+  // 1900 isn't a leap year, but 2000 is. Since JS two digits years to the Date constructor is an offset from the year 1900
+  // we need to special handle that case. For other cases it doesn't really matter if the year is 1925 or 2025.
+  if (year === 0) {
+    year = 2000;
+  }
+
+  // for a d-number the day is increased by 40. Eg the 31st of a month would be 71, or the 3rd would be 43.
+  // thus we need to subtract 40 to get the correct day of the month
+  if (day > 40) {
+    day = day - 40;
+  }
+
+  // important to use UTC so the user's timezone doesn't affect the validation
+  const date = new Date(Date.UTC(year, month - 1, day));
+
+  return date && date.getUTCMonth() === month - 1 && date.getUTCDate() === day;
+}

packages/validation/src/validation.test.ts

@@ -1,3 +1,4 @@
+import navfaker from 'nav-faker/dist/index';
 import { describe, expect, test } from 'vitest';
 import * as no from './no';
 import * as se from './se';
@@ -58,6 +59,54 @@ describe('no', () => {
   ])('validateObosMembershipNumber(%s) -> %s', (input, expected, options) => {
     expect(no.validateObosMembershipNumber(input, options)).toBe(expected);
   });
+
+  test('validateNationalIdentityNumber() - validates fødselsnummer', () => {
+    for (let i = 0; i < 1000; ++i) {
+      const fnr = navfaker.personIdentifikator.fødselsnummer();
+      expect(no.validateNationalIdentityNumber(fnr), `${fnr} is valid`).toBe(
+        true,
+      );
+    }
+  });
+
+  test('validateNationalIdentityNumber() - validates d-nummer', () => {
+    for (let i = 0; i < 1000; ++i) {
+      const dnr = navfaker.personIdentifikator.dnummer();
+      expect(no.validateNationalIdentityNumber(dnr), `${dnr} is valid`).toBe(
+        true,
+      );
+    }
+  });
+
+  test('validateNationalIdentityNumber() - validates leap years', () => {
+    expect(no.validateNationalIdentityNumber('29029648784')).toBe(true);
+  });
+
+  test('validateNationalIdentityNumber() - validates 00 as a leap year', () => {
+    expect(no.validateNationalIdentityNumber('29020075838')).toBe(true);
+  });
+
+  test('validateNationalIdentityNumber() - returns false for invalid identity numbers', () => {
+    expect(
+      no.validateNationalIdentityNumber('13097248032'),
+      '1st control digit is invalid',
+    ).toBe(false);
+
+    expect(
+      no.validateNationalIdentityNumber('13097248023'),
+      '2nd control digit is invalid',
+    ).toBe(false);
+
+    expect(
+      no.validateNationalIdentityNumber('32127248022'),
+      'day is invalid',
+    ).toBe(false);
+
+    expect(
+      no.validateNationalIdentityNumber('13137248022'),
+      'month is invalid',
+    ).toBe(false);
+  });
 });
 
 describe('se', () => {