Add date checking to f-numbers

index.js

@@ -4,10 +4,34 @@ function checkType (fodselsnummer) {
   return parseInt(fodselsnummer[0], 10) > 3 ? 'D' : 'F'
 }
 
+function hasValidDate (fodselsnummer) {
+  if (parseInt(fodselsnummer[0], 10) > 3) {
+    return true // skip date check for d-numbers
+  }
+  const d = parseInt(fodselsnummer.substr(0, 2))
+  const m = parseInt(fodselsnummer.substr(2, 2)) - 1
+  const y = parseInt(fodselsnummer.substr(4, 2))
+  const currentCentury = 2000
+  const yyyy = currentCentury + y
+  const date = new Date(yyyy, m, d)
+  const now = new Date()
+  const previousCenturyYYYY = yyyy - 100
+  if (date > now) return isValidDateValues(previousCenturyYYYY, m, d)
+  else return isValidDateValues(previousCenturyYYYY, m, d) || isValidDateValues(yyyy, m, d)
+}
+
+function isValidDateValues (yyyy, m, d) {
+  const date = new Date(yyyy, m, d)
+  return date.getFullYear() === yyyy && date.getMonth() === m && date.getDate() === d
+}
+
 module.exports = function (fodselsnummer, type) {
   if (fodselsnummer.length !== 11) {
     throw new Error('Too short. Expected length of 11.')
   }
+  if (!hasValidDate(fodselsnummer)) {
+    throw new Error('Invalid date for fodselsnummer.')
+  }
 
   var day = fodselsnummer.substr(0, 2)
   var month = fodselsnummer.substr(2, 2)

test/isValidFodselsnummer.js

@@ -9,8 +9,8 @@ tap.equal(
 )
 
 tap.equal(
-  false, isValidFodselsnummer('12341234567'),
-  '12341234567 is not a valid ID-number'
+  false, isValidFodselsnummer('11111234567'),
+  '11111234567 is not a valid ID-number'
 )
 
 tap.throws(
@@ -21,6 +21,14 @@ tap.throws(
   'Throws if number too short'
 )
 
+tap.throws(
+  function () {
+    isValidFodselsnummer('30029012311')
+  },
+  { message: 'Invalid date for fodselsnummer.' },
+  'Throws if number contains invalid date (for f-numbers only)'
+)
+
 tap.equal(
   true, isValidFodselsnummer('41085801188'),
   '41085801188 is a valid ID-number'
@@ -37,6 +45,6 @@ tap.equal(
 )
 
 tap.equal(
-  false, isValidFodselsnummer('12341234567', true),
-  '12341234567 is not a valid ID-number'
+  false, isValidFodselsnummer('11111234567', true),
+  '11111234567 is not a valid ID-number'
 )