toDate implementation fix

src/toDate/index.js

@@ -62,6 +62,7 @@ var patterns = {
  * @param {Options} [options] - the object with options. See [Options]{@link docs/Options}
  * @param {0|1|2} [options.additionalDigits=2] - the additional number of digits in the extended year format
  * @returns {Date} the parsed date in the local time zone
+ * @throws {RangeError} additionalDigits must be 0, 1 or 2
  *
  * @example
  * // Convert string '2014-02-11T11:30:30' to date:
@@ -75,6 +76,13 @@ var patterns = {
  * //=> Fri Apr 11 2014 00:00:00
  */
 export default function toDate (argument, dirtyOptions) {
+  var options = dirtyOptions || {}
+
+  var additionalDigits = options.additionalDigits === undefined ? DEFAULT_ADDITIONAL_DIGITS : Number(options.additionalDigits)
+  if (additionalDigits !== 2 && additionalDigits !== 1 && additionalDigits !== 0) {
+    throw new RangeError('additionalDigits must be 0, 1 or 2')
+  }
+
   // Clone the date
   if (isDate(argument)) {
     // Prevent the date to lose the milliseconds when passed to new Date() in IE10
@@ -83,14 +91,6 @@ export default function toDate (argument, dirtyOptions) {
     return new Date(argument)
   }
 
-  var options = dirtyOptions || {}
-  var additionalDigits = options.additionalDigits
-  if (additionalDigits == null) {
-    additionalDigits = DEFAULT_ADDITIONAL_DIGITS
-  } else {
-    additionalDigits = Number(additionalDigits)
-  }
-
   var dateStrings = splitDateString(argument)
 
   var parseYearResult = parseYear(dateStrings.date, additionalDigits)