Rename private attribute _element to _el

Change-Id: I9c7a31bd6844636737ffa6456562b997f5e370a3
diff --git a/dev/js/src/menu/item.js b/dev/js/src/menu/item.js
index 7ce7455..e369918 100644
--- a/dev/js/src/menu/item.js
+++ b/dev/js/src/menu/item.js
@@ -105,8 +105,8 @@
    */
   element : function () {
     // already defined
-    if (this._element !== undefined)
-      return this._element;
+    if (this._el !== undefined)
+      return this._el;
     
     // Create list item
     const li = document.createElement("li");
@@ -119,7 +119,7 @@
     // Append template
     li.appendChild(this.content());
     
-    return this._element = li;
+    return this._el = li;
   },
 
   /**