diff --git a/frontend-js/src/main/js/gui/AbstractGuiElement.js b/frontend-js/src/main/js/gui/AbstractGuiElement.js
index f2817d3a395badbdaf3103c8d5c39cbeb3974f00..970d3356401a727cc667a68558454fce6e3f7307 100644
--- a/frontend-js/src/main/js/gui/AbstractGuiElement.js
+++ b/frontend-js/src/main/js/gui/AbstractGuiElement.js
@@ -7,6 +7,13 @@ var PanelControlElementType = require('./PanelControlElementType');
 
 var logger = require('../logger');
 
+/**
+ *
+ * @param params
+ * @constructor
+ *
+ * @extends ObjectWithListeners
+ */
 function AbstractGuiElement(params) {
   ObjectWithListeners.call(this, params);
 
diff --git a/frontend-js/src/main/js/gui/Panel.js b/frontend-js/src/main/js/gui/Panel.js
index e58b7684dab9563de6037da12b6ba7c076d693f9..5d9f683e9556dc4d1c155959367597057e383ac8 100644
--- a/frontend-js/src/main/js/gui/Panel.js
+++ b/frontend-js/src/main/js/gui/Panel.js
@@ -11,6 +11,21 @@ var Functions = require('../Functions');
 var logger = require('../logger');
 var xss = require('xss');
 
+/**
+ *
+ * @param {Configuration} [params.configuration]
+ * @param {HTMLElement} params.element
+ * @param {Project} params.project
+ * @param {CustomMap} params.customMap
+ * @param {string} params.panelName
+ * @param {boolean} params.scrollable
+ * @param {string} [params.helpTip]
+ * @param params.parent
+ *
+ * @constructor
+ * @extends AbstractGuiElement
+ */
+
 function Panel(params) {
   AbstractGuiElement.call(this, params);
 
diff --git a/frontend-js/src/main/js/gui/admin/ChooseAnnotatorsDialog.js b/frontend-js/src/main/js/gui/admin/ChooseAnnotatorsDialog.js
index 2282b96c74a7b84883b7b53e89072cb71d27bc33..b0c74fefee6a3758cb0a1759c840fd329949aa32 100644
--- a/frontend-js/src/main/js/gui/admin/ChooseAnnotatorsDialog.js
+++ b/frontend-js/src/main/js/gui/admin/ChooseAnnotatorsDialog.js
@@ -317,7 +317,7 @@ ChooseAnnotatorsDialog.prototype.setElementType = function (elementType) {
                   });
                   paramValue.checked = (existingParamValue && existingParamValue === 'true');
                 } else {
-                  throw new InvalidAlgorithmError("Unknown annotator parameter type");
+                  throw new Error("Unknown annotator parameter type");
                 }
 
                 paramElement.appendChild(paramValue);
diff --git a/frontend-js/src/main/js/gui/leftPanel/AbstractDbPanel.js b/frontend-js/src/main/js/gui/leftPanel/AbstractDbPanel.js
index aa1d37c4c22dda29c27a669d80751b80b2a3199d..73fa48f126b94db5707701045588809b343fc77f 100644
--- a/frontend-js/src/main/js/gui/leftPanel/AbstractDbPanel.js
+++ b/frontend-js/src/main/js/gui/leftPanel/AbstractDbPanel.js
@@ -11,6 +11,13 @@ var PanelControlElementType = require('../PanelControlElementType');
 var logger = require('../../logger');
 var Functions = require('../../Functions');
 
+/**
+ *
+ * @param {string} params.placeholder
+ * @param {string} params.panelName
+ * @constructor
+ * @extends Panel
+ */
 function AbstractPanel(params) {
   Panel.call(this, params);
   var self = this;
@@ -170,6 +177,10 @@ AbstractPanel.prototype.setOverlayDb = function (overlayDb) {
   this._overlayDb = overlayDb;
 };
 
+/**
+ *
+ * @returns {AbstractDbOverlay}
+ */
 AbstractPanel.prototype.getOverlayDb = function () {
   return this._overlayDb;
 };
diff --git a/frontend-js/src/main/js/gui/leftPanel/ChemicalPanel.js b/frontend-js/src/main/js/gui/leftPanel/ChemicalPanel.js
index 35d60913fe28f1b620ed15f6df7d38d9914e3d4f..daff6715ab4bc0fd92fe0102c0a583acfa81254e 100644
--- a/frontend-js/src/main/js/gui/leftPanel/ChemicalPanel.js
+++ b/frontend-js/src/main/js/gui/leftPanel/ChemicalPanel.js
@@ -9,7 +9,12 @@ var logger = require('../../logger');
 var AbstractDbPanel = require('./AbstractDbPanel');
 var PanelControlElementType = require('../PanelControlElementType');
 
-
+/**
+ *
+ * @param params
+ * @constructor
+ * @extends AbstractDbPanel
+ */
 function ChemicalPanel(params) {
   var self = this;
   params.panelName = "chemical";