Minor ES6 improvements

Change-Id: Ibf956915d1b7769dc5cc22a870f4484f492da723
diff --git a/dev/js/src/session.js b/dev/js/src/session.js
index 27af76d..2211fe6 100644
--- a/dev/js/src/session.js
+++ b/dev/js/src/session.js
@@ -9,10 +9,8 @@
    * Create a new session.
    * Expects a name or defaults to 'korap'
    */
-  create : function (name) {
+  create : function (name = 'korap') {
     var obj = Object.create(this);
-    if (name === undefined)
-      name = 'korap';
     obj._name = name.toLowerCase();
     obj._hash = {};
     obj._parse();