diff --git a/src/wp-includes/js/customize-preview-nav-menus.js b/src/wp-includes/js/customize-preview-nav-menus.js
index 8f0b7df34a..017d1f1216 100644
--- a/src/wp-includes/js/customize-preview-nav-menus.js
+++ b/src/wp-includes/js/customize-preview-nav-menus.js
@@ -1,8 +1,12 @@
 /* global JSON, _wpCustomizePreviewNavMenusExports */
 
-wp.customize.menusPreview = ( function( $, api ) {
+( function( $, _, wp ) {
 	'use strict';
-	var currentRefreshDebounced = {},
+
+	if ( ! wp || ! wp.customize ) { return; }
+
+	var api = wp.customize,
+		currentRefreshDebounced = {},
 		refreshDebounceDelay = 200,
 		settings = {},
 		defaultSettings = {
@@ -16,265 +20,264 @@ wp.customize.menusPreview = ( function( $, api ) {
 				stylesheet: ''
 			},
 			navMenuInstanceArgs: {}
-		},
-		self = {};
-
-	api.bind( 'preview-ready', function() {
-		api.preview.bind( 'active', function() {
-			self.init();
-		} );
-	} );
-
-	/**
-	 * Bootstrap functionality.
-	 */
-	self.init = function() {
-		var self = this, initializedSettings = {};
-
-		settings = _.extend( {}, defaultSettings );
-		if ( 'undefined' !== typeof _wpCustomizePreviewNavMenusExports ) {
-			_.extend( settings, _wpCustomizePreviewNavMenusExports );
-		}
-
-		api.each( function( setting, id ) {
-			setting.id = id;
-			initializedSettings[ setting.id ] = true;
-			self.bindListener( setting );
-		} );
-
-		api.preview.bind( 'setting', function( args ) {
-			var id, value, setting;
-			args = args.slice();
-			id = args.shift();
-			value = args.shift();
-
-			setting = api( id );
-			if ( ! setting ) {
-				// Currently customize-preview.js is not creating settings for dynamically-created settings in the pane, so we have to do it.
-				setting = api.create( id, value ); // @todo This should be in core
-			}
-			if ( ! setting.id ) {
-				// Currently customize-preview.js doesn't set the id property for each setting, like customize-controls.js does.
-				setting.id = id;
-			}
-
-			if ( ! initializedSettings[ setting.id ] ) {
-				initializedSettings[ setting.id ] = true;
-				if ( self.bindListener( setting ) ) {
-					setting.callbacks.fireWith( setting, [ setting(), null ] );
-				}
-			}
-		} );
-	};
-
-	/**
-	 *
-	 * @param {wp.customize.Value} setting
-	 * @returns {boolean} Whether the setting was bound.
-	 */
-	self.bindListener = function( setting ) {
-		var matches, themeLocation;
-
-		matches = setting.id.match( /^nav_menu\[(-?\d+)]$/ );
-		if ( matches ) {
-			setting.navMenuId = parseInt( matches[1], 10 );
-			setting.bind( self.onChangeNavMenuSetting );
-			return true;
-		}
-
-		matches = setting.id.match( /^nav_menu_item\[(-?\d+)]$/ );
-		if ( matches ) {
-			setting.navMenuItemId = parseInt( matches[1], 10 );
-			setting.bind( self.onChangeNavMenuItemSetting );
-			return true;
-		}
-
-		matches = setting.id.match( /^nav_menu_locations\[(.+?)]/ );
-		if ( matches ) {
-			themeLocation = matches[1];
-			setting.bind( function() {
-				self.refreshMenuLocation( themeLocation );
-			} );
-			return true;
-		}
-
-		return false;
-	};
-
-	/**
-	 * Handle changing of a nav_menu setting.
-	 *
-	 * @this {wp.customize.Setting}
-	 */
-	self.onChangeNavMenuSetting = function() {
-		var setting = this;
-		if ( ! setting.navMenuId ) {
-			throw new Error( 'Expected navMenuId property to be set.' );
-		}
-		self.refreshMenu( setting.navMenuId );
-	};
-
-	/**
-	 * Handle changing of a nav_menu_item setting.
-	 *
-	 * @this {wp.customize.Setting}
-	 * @param {object} to
-	 * @param {object} from
-	 */
-	self.onChangeNavMenuItemSetting = function( to, from ) {
-		if ( from && from.nav_menu_term_id && ( ! to || from.nav_menu_term_id !== to.nav_menu_term_id ) ) {
-			self.refreshMenu( from.nav_menu_term_id );
-		}
-		if ( to && to.nav_menu_term_id ) {
-			self.refreshMenu( to.nav_menu_term_id );
-		}
-	};
-
-	/**
-	 * Update a given menu rendered in the preview.
-	 *
-	 * @param {int} menuId
-	 */
-	self.refreshMenu = function( menuId ) {
-		var assignedLocations = [];
-
-		api.each(function( setting, id ) {
-			var matches = id.match( /^nav_menu_locations\[(.+?)]/ );
-			if ( matches && menuId === setting() ) {
-				assignedLocations.push( matches[1] );
-			}
-		});
-
-		_.each( settings.navMenuInstanceArgs, function( navMenuArgs, instanceNumber ) {
-			if ( menuId === navMenuArgs.menu || -1 !== _.indexOf( assignedLocations, navMenuArgs.theme_location ) ) {
-				this.refreshMenuInstanceDebounced( instanceNumber );
-			}
-		}, this );
-	};
-
-	/**
-	 * Refresh the menu(s) associated with a given nav menu location.
-	 *
-	 * @param {string} location
-	 */
-	self.refreshMenuLocation = function( location ) {
-		var foundInstance = false;
-		_.each( settings.navMenuInstanceArgs, function( navMenuArgs, instanceNumber ) {
-			if ( location === navMenuArgs.theme_location ) {
-				this.refreshMenuInstanceDebounced( instanceNumber );
-				foundInstance = true;
-			}
-		}, this );
-		if ( ! foundInstance ) {
-			api.preview.send( 'refresh' );
-		}
-	};
-
-	/**
-	 * Update a specific instance of a given menu on the page.
-	 *
-	 * @param {int} instanceNumber
-	 */
-	self.refreshMenuInstance = function( instanceNumber ) {
-		var self = this, data, menuId, customized, container, request, wpNavArgs, instance, containerInstanceClassName;
-
-		if ( ! settings.navMenuInstanceArgs[ instanceNumber ] ) {
-			throw new Error( 'unknown_instance_number' );
-		}
-		instance = settings.navMenuInstanceArgs[ instanceNumber ];
-
-		containerInstanceClassName = 'partial-refreshable-nav-menu-' + String( instanceNumber );
-		container = $( '.' + containerInstanceClassName );
-
-		if ( _.isNumber( instance.menu ) ) {
-			menuId = instance.menu;
-		} else if ( instance.theme_location && api.has( 'nav_menu_locations[' + instance.theme_location + ']' ) ) {
-			menuId = api( 'nav_menu_locations[' + instance.theme_location + ']' ).get();
-		}
-
-		if ( ! menuId || ! instance.can_partial_refresh || 0 === container.length ) {
-			api.preview.send( 'refresh' );
-			return;
-		}
-		menuId = parseInt( menuId, 10 );
-
-		data = {
-			nonce: settings.previewCustomizeNonce, // for Customize Preview
-			wp_customize: 'on'
 		};
-		if ( ! settings.theme.active ) {
-			data.theme = settings.theme.stylesheet;
-		}
-		data[ settings.renderQueryVar ] = '1';
 
-		// Gather settings to send in partial refresh request.
-		customized = {};
-		api.each( function( setting, id ) {
-			var value = setting.get(), shouldSend = false;
-			// @todo Core should propagate the dirty state into the Preview as well so we can use that here.
+	api.MenusCustomizerPreview = {
+		/**
+		 * Bootstrap functionality.
+		 */
+		init : function() {
+			var self = this, initializedSettings = {};
 
-			// Send setting if it is a nav_menu_locations[] setting.
-			shouldSend = shouldSend || /^nav_menu_locations\[/.test( id );
-
-			// Send setting if it is the setting for this menu.
-			shouldSend = shouldSend || id === 'nav_menu[' + String( menuId ) + ']';
-
-			// Send setting if it is one that is associated with this menu, or it is deleted.
-			shouldSend = shouldSend || ( /^nav_menu_item\[/.test( id ) && ( false === value || menuId === value.nav_menu_term_id ) );
-
-			if ( shouldSend ) {
-				customized[ id ] = value;
+			settings = _.extend( {}, defaultSettings );
+			if ( 'undefined' !== typeof _wpCustomizePreviewNavMenusExports ) {
+				_.extend( settings, _wpCustomizePreviewNavMenusExports );
 			}
-		} );
-		data.customized = JSON.stringify( customized );
-		data[ settings.renderNoncePostKey ] = settings.renderNonceValue;
 
-		wpNavArgs = $.extend( {}, instance );
-		data.wp_nav_menu_args_hash = wpNavArgs.args_hash;
-		delete wpNavArgs.args_hash;
-		data.wp_nav_menu_args = JSON.stringify( wpNavArgs );
+			api.each( function( setting, id ) {
+				setting.id = id;
+				initializedSettings[ setting.id ] = true;
+				self.bindListener( setting );
+			} );
 
-		container.addClass( 'customize-partial-refreshing' );
+			api.preview.bind( 'setting', function( args ) {
+				var id, value, setting;
+				args = args.slice();
+				id = args.shift();
+				value = args.shift();
 
-		request = wp.ajax.send( null, {
-			data: data,
-			url: settings.requestUri
-		} );
-		request.done( function( data ) {
-			// If the menu is now not visible, refresh since the page layout may have changed.
-			if ( false === data ) {
+				setting = api( id );
+				if ( ! setting ) {
+					// Currently customize-preview.js is not creating settings for dynamically-created settings in the pane, so we have to do it.
+					setting = api.create( id, value ); // @todo This should be in core
+				}
+				if ( ! setting.id ) {
+					// Currently customize-preview.js doesn't set the id property for each setting, like customize-controls.js does.
+					setting.id = id;
+				}
+
+				if ( ! initializedSettings[ setting.id ] ) {
+					initializedSettings[ setting.id ] = true;
+					if ( self.bindListener( setting ) ) {
+						setting.callbacks.fireWith( setting, [ setting(), null ] );
+					}
+				}
+			} );
+		},
+
+		/**
+		 *
+		 * @param {wp.customize.Value} setting
+		 * @returns {boolean} Whether the setting was bound.
+		 */
+		bindListener : function( setting ) {
+			var matches, themeLocation;
+
+			matches = setting.id.match( /^nav_menu\[(-?\d+)]$/ );
+			if ( matches ) {
+				setting.navMenuId = parseInt( matches[1], 10 );
+				setting.bind( this.onChangeNavMenuSetting );
+				return true;
+			}
+
+			matches = setting.id.match( /^nav_menu_item\[(-?\d+)]$/ );
+			if ( matches ) {
+				setting.navMenuItemId = parseInt( matches[1], 10 );
+				setting.bind( this.onChangeNavMenuItemSetting );
+				return true;
+			}
+
+			matches = setting.id.match( /^nav_menu_locations\[(.+?)]/ );
+			if ( matches ) {
+				themeLocation = matches[1];
+				setting.bind( _.bind( function() {
+					this.refreshMenuLocation( themeLocation );
+				}, this ) );
+				return true;
+			}
+
+			return false;
+		},
+
+		/**
+		 * Handle changing of a nav_menu setting.
+		 *
+		 * @this {wp.customize.Setting}
+		 */
+		onChangeNavMenuSetting : function() {
+			var setting = this;
+			if ( ! setting.navMenuId ) {
+				throw new Error( 'Expected navMenuId property to be set.' );
+			}
+			api.MenusCustomizerPreview.refreshMenu( setting.navMenuId );
+		},
+
+		/**
+		 * Handle changing of a nav_menu_item setting.
+		 *
+		 * @this {wp.customize.Setting}
+		 * @param {object} to
+		 * @param {object} from
+		 */
+		onChangeNavMenuItemSetting : function( to, from ) {
+			if ( from && from.nav_menu_term_id && ( ! to || from.nav_menu_term_id !== to.nav_menu_term_id ) ) {
+				api.MenusCustomizerPreview.refreshMenu( from.nav_menu_term_id );
+			}
+			if ( to && to.nav_menu_term_id ) {
+				api.MenusCustomizerPreview.refreshMenu( to.nav_menu_term_id );
+			}
+		},
+
+		/**
+		 * Update a given menu rendered in the preview.
+		 *
+		 * @param {int} menuId
+		 */
+		refreshMenu : function( menuId ) {
+			var assignedLocations = [];
+
+			api.each(function( setting, id ) {
+				var matches = id.match( /^nav_menu_locations\[(.+?)]/ );
+				if ( matches && menuId === setting() ) {
+					assignedLocations.push( matches[1] );
+				}
+			});
+
+			_.each( settings.navMenuInstanceArgs, function( navMenuArgs, instanceNumber ) {
+				if ( menuId === navMenuArgs.menu || -1 !== _.indexOf( assignedLocations, navMenuArgs.theme_location ) ) {
+					this.refreshMenuInstanceDebounced( instanceNumber );
+				}
+			}, this );
+		},
+
+		/**
+		 * Refresh the menu(s) associated with a given nav menu location.
+		 *
+		 * @param {string} location
+		 */
+		refreshMenuLocation : function( location ) {
+			var foundInstance = false;
+			_.each( settings.navMenuInstanceArgs, function( navMenuArgs, instanceNumber ) {
+				if ( location === navMenuArgs.theme_location ) {
+					this.refreshMenuInstanceDebounced( instanceNumber );
+					foundInstance = true;
+				}
+			}, this );
+			if ( ! foundInstance ) {
+				api.preview.send( 'refresh' );
+			}
+		},
+
+		/**
+		 * Update a specific instance of a given menu on the page.
+		 *
+		 * @param {int} instanceNumber
+		 */
+		refreshMenuInstance : function( instanceNumber ) {
+			var data, menuId, customized, container, request, wpNavArgs, instance, containerInstanceClassName;
+
+			if ( ! settings.navMenuInstanceArgs[ instanceNumber ] ) {
+				throw new Error( 'unknown_instance_number' );
+			}
+			instance = settings.navMenuInstanceArgs[ instanceNumber ];
+
+			containerInstanceClassName = 'partial-refreshable-nav-menu-' + String( instanceNumber );
+			container = $( '.' + containerInstanceClassName );
+
+			if ( _.isNumber( instance.menu ) ) {
+				menuId = instance.menu;
+			} else if ( instance.theme_location && api.has( 'nav_menu_locations[' + instance.theme_location + ']' ) ) {
+				menuId = api( 'nav_menu_locations[' + instance.theme_location + ']' ).get();
+			}
+
+			if ( ! menuId || ! instance.can_partial_refresh || 0 === container.length ) {
 				api.preview.send( 'refresh' );
 				return;
 			}
+			menuId = parseInt( menuId, 10 );
 
-			var eventParam, previousContainer = container;
-			container = $( data );
-			container.addClass( containerInstanceClassName );
-			container.addClass( 'partial-refreshable-nav-menu customize-partial-refreshing' );
-			previousContainer.replaceWith( container );
-			eventParam = {
-				instanceNumber: instanceNumber,
-				wpNavArgs: wpNavArgs,
-				oldContainer: previousContainer,
-				newContainer: container
+			data = {
+				nonce: settings.previewCustomizeNonce, // for Customize Preview
+				wp_customize: 'on'
 			};
-			container.removeClass( 'customize-partial-refreshing' );
-			$( document ).trigger( 'customize-preview-menu-refreshed', [ eventParam ] );
-		} );
-	};
+			if ( ! settings.theme.active ) {
+				data.theme = settings.theme.stylesheet;
+			}
+			data[ settings.renderQueryVar ] = '1';
 
-	self.refreshMenuInstanceDebounced = function( instanceNumber ) {
-		if ( currentRefreshDebounced[ instanceNumber ] ) {
-			clearTimeout( currentRefreshDebounced[ instanceNumber ] );
+			// Gather settings to send in partial refresh request.
+			customized = {};
+			api.each( function( setting, id ) {
+				var value = setting.get(), shouldSend = false;
+				// @todo Core should propagate the dirty state into the Preview as well so we can use that here.
+
+				// Send setting if it is a nav_menu_locations[] setting.
+				shouldSend = shouldSend || /^nav_menu_locations\[/.test( id );
+
+				// Send setting if it is the setting for this menu.
+				shouldSend = shouldSend || id === 'nav_menu[' + String( menuId ) + ']';
+
+				// Send setting if it is one that is associated with this menu, or it is deleted.
+				shouldSend = shouldSend || ( /^nav_menu_item\[/.test( id ) && ( false === value || menuId === value.nav_menu_term_id ) );
+
+				if ( shouldSend ) {
+					customized[ id ] = value;
+				}
+			} );
+			data.customized = JSON.stringify( customized );
+			data[ settings.renderNoncePostKey ] = settings.renderNonceValue;
+
+			wpNavArgs = $.extend( {}, instance );
+			data.wp_nav_menu_args_hash = wpNavArgs.args_hash;
+			delete wpNavArgs.args_hash;
+			data.wp_nav_menu_args = JSON.stringify( wpNavArgs );
+
+			container.addClass( 'customize-partial-refreshing' );
+
+			request = wp.ajax.send( null, {
+				data: data,
+				url: settings.requestUri
+			} );
+			request.done( function( data ) {
+				// If the menu is now not visible, refresh since the page layout may have changed.
+				if ( false === data ) {
+					api.preview.send( 'refresh' );
+					return;
+				}
+
+				var eventParam, previousContainer = container;
+				container = $( data );
+				container.addClass( containerInstanceClassName );
+				container.addClass( 'partial-refreshable-nav-menu customize-partial-refreshing' );
+				previousContainer.replaceWith( container );
+				eventParam = {
+					instanceNumber: instanceNumber,
+					wpNavArgs: wpNavArgs,
+					oldContainer: previousContainer,
+					newContainer: container
+				};
+				container.removeClass( 'customize-partial-refreshing' );
+				$( document ).trigger( 'customize-preview-menu-refreshed', [ eventParam ] );
+			} );
+		},
+
+		refreshMenuInstanceDebounced : function( instanceNumber ) {
+			if ( currentRefreshDebounced[ instanceNumber ] ) {
+				clearTimeout( currentRefreshDebounced[ instanceNumber ] );
+			}
+			currentRefreshDebounced[ instanceNumber ] = setTimeout(
+				_.bind( function() {
+					this.refreshMenuInstance( instanceNumber );
+				}, this ),
+				refreshDebounceDelay
+			);
 		}
-		currentRefreshDebounced[ instanceNumber ] = setTimeout(
-			function() {
-				self.refreshMenuInstance( instanceNumber );
-			},
-			refreshDebounceDelay
-		);
 	};
 
-	return self;
+	api.bind( 'preview-ready', function() {
+		api.preview.bind( 'active', function() {
+			api.MenusCustomizerPreview.init();
+		} );
+	} );
 
-}( jQuery, wp.customize ) );
+}( jQuery, _, wp ) );