diff --git a/IPython/html/static/notebook/js/widgetmanager.js b/IPython/html/static/notebook/js/widgetmanager.js
index e2dfe20..6b3dfa5 100644
--- a/IPython/html/static/notebook/js/widgetmanager.js
+++ b/IPython/html/static/notebook/js/widgetmanager.js
@@ -34,14 +34,12 @@
 
             // Attach a comm manager to the 
             this.comm_manager = comm_manager;
+            this._models = {}; /* Dictionary of model ids and model instances */
 
             // Register already-registered widget model types with the comm manager.
-            for (var name in WidgetManager._model_types) {
-                if (WidgetManager._model_types.hasOwnProperty(name)) {
-                    this.comm_manager.register_target(name, $.proxy(this._handle_comm_open, this));
-
-                }
-            }
+            _.each(WidgetManager._model_types, function(value, key) {
+                this.comm_manager.register_target(value, $.proxy(this._handle_comm_open, this));
+            });
         };
 
         //--------------------------------------------------------------------
@@ -49,7 +47,6 @@
         //--------------------------------------------------------------------
         WidgetManager._model_types = {}; /* Dictionary of model type names (target_name) and model types. */
         WidgetManager._view_types = {}; /* Dictionary of view names and view types. */
-        WidgetManager._models = {}; /* Dictionary of model ids and model instances */
         WidgetManager._managers = []; /* List of widget managers */
 
         WidgetManager.register_widget_model = function (model_name, model_type) {
@@ -58,12 +55,11 @@
 
             // Register the widget with the comm manager.  Make sure to pass this object's context
             // in so `this` works in the call back.
-            for (var i = 0; i < WidgetManager._managers.length; i++) {
-                var instance = WidgetManager._managers[i];
+            _.each(WidgetManager._managers, function(instance, i) {
                 if (instance.comm_manager !== null) {
                     instance.comm_manager.register_target(model_name, $.proxy(instance._handle_comm_open, instance));
                 }
-            }
+            });
         };
 
         WidgetManager.register_widget_view = function (view_name, view_type) {
@@ -169,7 +165,7 @@
         };
 
         WidgetManager.prototype.get_model = function (model_id) {
-            var model = WidgetManager._models[model_id];
+            var model = this._models[model_id];
             if (model !== undefined && model.id == model_id) {
                 return model;
             }
@@ -180,7 +176,7 @@
             var model_id = comm.comm_id;
             var widget_type_name = msg.content.target_name;
             var widget_model = new WidgetManager._model_types[widget_type_name](this, model_id, comm);
-            WidgetManager._models[model_id] = widget_model;
+            this._models[model_id] = widget_model;
         };
         
         IPython.WidgetManager = WidgetManager;
diff --git a/IPython/html/static/notebook/js/widgets/widget.js b/IPython/html/static/notebook/js/widgets/widget.js
index a6ac027..9a23283 100644
--- a/IPython/html/static/notebook/js/widgets/widget.js
+++ b/IPython/html/static/notebook/js/widgets/widget.js
@@ -86,17 +86,14 @@ function(WidgetManager, Underscore, Backbone){
 
         apply_update: function (state) {
             // Handle when a widget is updated via the python side.
-            for (var key in state) {
-                if (state.hasOwnProperty(key)) {
-                    var value = state[key];
-                    this.key_value_lock = [key, value];
-                    try {
-                        this.set(key, this._unpack_models(value));
-                    } finally {
-                        this.key_value_lock = null;
-                    }
+            _.each(state, function(value, key) {
+                this.key_value_lock = [key, value];
+                try {
+                    this.set(key, this._unpack_models(value));
+                } finally {
+                    this.key_value_lock = null;
                 }
-            }
+            });
         },
 
         _handle_status: function (msg, callbacks) {
@@ -205,9 +202,9 @@ function(WidgetManager, Underscore, Backbone){
                 return value.id;
             } else if (value instanceof Object) {
                 var packed = {};
-                for (var key in value) {
-                    packed[key] = this._pack_models(value[key]);
-                }
+                _.each(value, function(sub_value, key) {
+                    packed[key] = this._pack_models(sub_value);
+                });
                 return packed;
             } else {
                 return value;
@@ -218,9 +215,9 @@ function(WidgetManager, Underscore, Backbone){
             // Replace model ids with models recursively.
             if (value instanceof Object) {
                 var unpacked = {};
-                for (var key in value) {
-                    unpacked[key] = this._unpack_models(value[key]);
-                }
+                _.each(value, function(sub_value, key) {
+                    unpacked[key] = this._unpack_models(sub_value);
+                });
                 return unpacked;
             } else {
                 var model = this.widget_manager.get_model(value);
@@ -369,20 +366,16 @@ function(WidgetManager, Underscore, Backbone){
      
             var css = this.model.get('_css');
             if (css === undefined) {return;}
-            for (var selector in css) {
-                if (css.hasOwnProperty(selector)) {
-                    // Apply the css traits to all elements that match the selector.
-                    var elements = this._get_selector_element(selector);
-                    if (elements.length > 0) {
-                        var css_traits = css[selector];    
-                        for (var css_key in css_traits) {
-                            if (css_traits.hasOwnProperty(css_key)) {
-                                elements.css(css_key, css_traits[css_key]);
-                            }
-                        }
-                    }
+            _.each(css, function(css_traits, selector){
+                // Apply the css traits to all elements that match the selector.
+                var elements = this._get_selector_element(selector);
+                if (elements.length > 0) {
+                    _.each(css_traits, function(css_value, css_key){
+                        elements.css(css_key, css_value);
+                    });
                 }
-            }
+            });
+                    
         },
 
         _get_selector_element: function (selector) {
diff --git a/IPython/html/static/notebook/js/widgets/widget_float_range.js b/IPython/html/static/notebook/js/widgets/widget_float_range.js
index 37c1095..fd59ba2 100644
--- a/IPython/html/static/notebook/js/widgets/widget_float_range.js
+++ b/IPython/html/static/notebook/js/widgets/widget_float_range.js
@@ -50,12 +50,12 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
                 // JQuery slider option keys.  These keys happen to have a
                 // one-to-one mapping with the corrosponding keys of the model.
                 var jquery_slider_keys = ['step', 'max', 'min', 'disabled'];
-                for (var index in jquery_slider_keys) {
-                    var key = jquery_slider_keys[index];
-                    if (this.model.get(key) !== undefined) {
-                        this.$slider.slider("option", key, this.model.get(key));
+                _.each(jquery_slider_keys, function(key, i) {
+                    var model_value = this.model.get(key);
+                    if (model_value !== undefined) {
+                        this.$slider.slider("option", key, model_value);
                     }
-                }
+                });
 
                 // WORKAROUND FOR JQUERY SLIDER BUG.
                 // The horizontal position of the slider handle
diff --git a/IPython/html/static/notebook/js/widgets/widget_int_range.js b/IPython/html/static/notebook/js/widgets/widget_int_range.js
index f01109b..7d26aec 100644
--- a/IPython/html/static/notebook/js/widgets/widget_int_range.js
+++ b/IPython/html/static/notebook/js/widgets/widget_int_range.js
@@ -49,12 +49,12 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
                 // JQuery slider option keys.  These keys happen to have a
                 // one-to-one mapping with the corrosponding keys of the model.
                 var jquery_slider_keys = ['step', 'max', 'min', 'disabled'];
-                for (var index in jquery_slider_keys) {
-                    var key = jquery_slider_keys[index];
-                    if (this.model.get(key) !== undefined) {
-                        this.$slider.slider("option", key, this.model.get(key));
+                _.each(jquery_slider_keys, function(key, i) {
+                    var model_value = this.model.get(key);
+                    if (model_value !== undefined) {
+                        this.$slider.slider("option", key, model_value);
                     }
-                }
+                });
 
                 // WORKAROUND FOR JQUERY SLIDER BUG.
                 // The horizontal position of the slider handle
diff --git a/IPython/html/static/notebook/js/widgets/widget_selection.js b/IPython/html/static/notebook/js/widgets/widget_selection.js
index db35626..c95e34b 100644
--- a/IPython/html/static/notebook/js/widgets/widget_selection.js
+++ b/IPython/html/static/notebook/js/widgets/widget_selection.js
@@ -67,13 +67,13 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
                 var items = this.model.get('values');
                 var $replace_droplist = $('<ul />')
                     .addClass('dropdown-menu');
-                for (var index in items) {
-                    var that = this;
+                _.each(items, function(item, i) {
                     var item_button = $('<a href="#"/>')
-                        .text(items[index])
+                        .text(item)
                         .on('click', $.proxy(this.handle_click, this));
                     $replace_droplist.append($('<li />').append(item_button));
-                }
+                });
+
                 this.$droplist.replaceWith($replace_droplist);
                 this.$droplist.remove();
                 this.$droplist = $replace_droplist;
@@ -140,41 +140,41 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
                 // Add missing items to the DOM.
                 var items = this.model.get('values');
                 var disabled = this.model.get('disabled');
-                for (var index in items) {
-                    var item_query = ' :input[value="' + items[index] + '"]';
+                _.each(items, function(item, index) {
+                    var item_query = ' :input[value="' + item + '"]';
                     if (this.$el.find(item_query).length === 0) {
                         var $label = $('<label />')
                             .addClass('radio')
-                            .text(items[index])
+                            .text(item)
                             .appendTo(this.$container);
                         
                         $('<input />')
                             .attr('type', 'radio')
                             .addClass(this.model)
-                            .val(items[index])
+                            .val(item)
                             .prependTo($label)
                             .on('click', $.proxy(this.handle_click, this));
                     }
                     
                     var $item_element = this.$container.find(item_query);
-                    if (this.model.get('value') == items[index]) {
+                    if (this.model.get('value') == item) {
                         $item_element.prop('checked', true);
                     } else {
                         $item_element.prop('checked', false);
                     }
                     $item_element.prop('disabled', disabled);
-                }
+                });
                 
                 // Remove items that no longer exist.
                 this.$container.find('input').each(function(i, obj) {
                     var value = $(obj).val();
                     var found = false;
-                    for (var index in items) {
-                        if (items[index] == value) {
+                    _.each(items, function(item, index) {
+                        if (item == value) {
                             found = true;
                             break;
                         }
-                    }
+                    });
                     
                     if (!found) {
                         $(obj).parent().remove();
@@ -230,37 +230,37 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
                 // Add missing items to the DOM.
                 var items = this.model.get('values');
                 var disabled = this.model.get('disabled');
-                for (var index in items) {
-                    var item_query = ' :contains("' + items[index] + '")';
+                _.each(items, function(item, index) {
+                   var item_query = ' :contains("' + item + '")';
                     if (this.$buttongroup.find(item_query).length === 0) {
                         $('<button />')
                             .attr('type', 'button')
                             .addClass('btn')
-                            .text(items[index])
+                            .text(item)
                             .appendTo(this.$buttongroup)
                             .on('click', $.proxy(this.handle_click, this));
                     }
                     
                     var $item_element = this.$buttongroup.find(item_query);
-                    if (this.model.get('value') == items[index]) {
+                    if (this.model.get('value') == item) {
                         $item_element.addClass('active');
                     } else {
                         $item_element.removeClass('active');
                     }
-                    $item_element.prop('disabled', disabled);
-                }
+                    $item_element.prop('disabled', disabled); 
+                });
                 
                 // Remove items that no longer exist.
                 this.$buttongroup.find('button').each(function(i, obj) {
                     var value = $(obj).text();
                     var found = false;
-                    for (var index in items) {
-                        if (items[index] == value) {
+                    _.each(items, function(item, index) {
+                        if (item == value) {
                             found = true;
                             break;
                         }
-                    }
-                    
+                    });
+
                     if (!found) {
                         $(obj).remove();
                     }
@@ -314,16 +314,16 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
             if (options === undefined || options.updated_view != this) {
                 // Add missing items to the DOM.
                 var items = this.model.get('values');
-                for (var index in items) {
-                    var item_query = ' :contains("' + items[index] + '")';
+                _.each(items, function(item, index) {
+                   var item_query = ' :contains("' + item + '")';
                     if (this.$listbox.find(item_query).length === 0) {
                         $('<option />')
-                            .text(items[index])
-                            .attr('value', items[index])
+                            .text(item)
+                            .attr('value', item)
                             .appendTo(this.$listbox)
                             .on('click', $.proxy(this.handle_click, this));
-                    }
-                }
+                    } 
+                });
 
                 // Select the correct element
                 this.$listbox.val(this.model.get('value'));
@@ -336,12 +336,12 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
                 this.$listbox.find('option').each(function(i, obj) {
                     var value = $(obj).text();
                     var found = false;
-                    for (var index in items) {
-                        if (items[index] == value) {
+                    _.each(items, function(item, index) {
+                        if (item == value) {
                             found = true;
                             break;
                         }
-                    }
+                    });
                     
                     if (!found) {
                         $(obj).remove();
diff --git a/IPython/html/static/notebook/js/widgets/widget_selectioncontainer.js b/IPython/html/static/notebook/js/widgets/widget_selectioncontainer.js
index bff6efc..283378f 100644
--- a/IPython/html/static/notebook/js/widgets/widget_selectioncontainer.js
+++ b/IPython/html/static/notebook/js/widgets/widget_selectioncontainer.js
@@ -39,28 +39,26 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
             if (options === undefined || options.updated_view != this) {
                 // Set tab titles
                 var titles = this.model.get('_titles');
-                for (var page_index in titles) {
-
+                _.each(titles, function(title, page_index) {
                     var accordian = this.containers[page_index];
                     if (accordian !== undefined) {
                         accordian
                             .find('.accordion-heading')
                             .find('.accordion-toggle')
-                            .text(titles[page_index]);
+                            .text(title);
                     }
-                }
+                });
 
                 // Set selected page
                 var selected_index = this.model.get("selected_index");
                 if (0 <= selected_index && selected_index < this.containers.length) {
-                    for (var index in this.containers) {
+                    _.each(this.containers, function(container, index) {
                         if (index==selected_index) {
-                            this.containers[index].find('.accordion-body').collapse('show');    
+                            container.find('.accordion-body').collapse('show');    
                         } else {
-                            this.containers[index].find('.accordion-body').collapse('hide');    
+                            container.find('.accordion-body').collapse('hide');    
                         }
-                        
-                    }
+                    });
                 }
             }
             return AccordionView.__super__.update.apply(this);
@@ -218,12 +216,12 @@ define(["notebook/js/widgets/widget"], function(WidgetManager){
             if (options === undefined || options.updated_view != this) {
                 // Set tab titles
                 var titles = this.model.get('_titles');
-                for (var page_index in titles) {
-                    var tab_text = this.containers[page_index];
+                _.each(titles, function(title, page_index) {
+                   var tab_text = this.containers[page_index];
                     if (tab_text !== undefined) {
-                        tab_text.text(titles[page_index]);
-                    }
-                }
+                        tab_text.text(title);
+                    } 
+                });
 
                 var selected_index = this.model.get('selected_index');
                 if (0 <= selected_index && selected_index < this.containers.length) {