Minor fixes and polyfills

UI/polyfills.js

@@ -0,0 +1,32 @@
+if (!String.prototype.startsWith) {
+    Object.defineProperty(String.prototype, 'startsWith', {
+        enumerable: false,
+        configurable: false,
+        writable: false,
+        value: function (searchString, position) {
+            position = position || 0;
+            return this.indexOf(searchString, position) === position;
+        }
+    });
+}
+
+if (!String.prototype.endsWith) {
+    Object.defineProperty(String.prototype, 'endsWith', {
+        enumerable: false,
+        configurable: false,
+        writable: false,
+        value: function (searchString, position) {
+            position = position || this.length;
+            position = position - searchString.length;
+            var lastIndex = this.lastIndexOf(searchString);
+            return lastIndex !== -1 && lastIndex === position;
+        }
+    });
+}
+
+if(!('contains' in String.prototype))
+{
+    String.prototype.contains = function(str, startIndex) {
+        return -1 !== String.prototype.indexOf.call(this, str, startIndex);
+    };
+}