refactor: implement suggestion from #2019 review

Author: WikiRik

src/lib/isAfter.js

@@ -4,18 +4,9 @@ import toDate from './toDate';
 export default function isAfter(str, options) {
   assertString(str);
 
-  let date;
-
-  if (typeof (options) === 'object') {
-    date = options.date;
-  } else { // backwards compatibility: isAfter(str [, date])
-    // eslint-disable-next-line prefer-rest-params
-    date = arguments[1];
-  }
-
-  if (!date) {
-    date = String(new Date());
-  }
+  // accessing 'arguments' for backwards compatibility: isAfter(str [, date])
+  // eslint-disable-next-line prefer-rest-params
+  const date = (typeof options === 'object' ? options.date : arguments[1]) || String(new Date());
 
   const comparison = toDate(date);
   const original = toDate(str);