Cleanup and simplify JS code

Change-Id: I393e22763c1a1d18878026bf459b747b150429fb
diff --git a/dev/js/src/util.js b/dev/js/src/util.js
index 719c889..5b6c8f8 100644
--- a/dev/js/src/util.js
+++ b/dev/js/src/util.js
@@ -32,11 +32,12 @@
   };
 };
 
-
+// Append element by tag name
 HTMLElement.prototype.addE = function (tag) {
   return this.appendChild(document.createElement(tag));
 };
 
+// Append text node
 HTMLElement.prototype.addT = function (text) {
   return this.appendChild(document.createTextNode(text));
 };
@@ -64,7 +65,7 @@
   KorAP.API = KorAP.API || {};
   KorAP.Locale = KorAP.Locale || {};
 
-  var loc = KorAP.Locale;
+  const loc = KorAP.Locale;
   loc.OR  = loc.OR  || 'or';
   loc.AND = loc.AND || 'and';