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wp-includes/js/customize-selective-refresh.js

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+/* global jQuery, JSON, _customizePartialRefreshExports, console */
+
+wp.customize.selectiveRefresh = ( function( $, api ) {
+	'use strict';
+	var self, Partial, Placement;
+
+	self = {
+		ready: $.Deferred(),
+		data: {
+			partials: {},
+			renderQueryVar: '',
+			l10n: {
+				shiftClickToEdit: ''
+			},
+			refreshBuffer: 250
+		},
+		currentRequest: null
+	};
+
+	_.extend( self, api.Events );
+
+	/**
+	 * A Customizer Partial.
+	 *
+	 * A partial provides a rendering of one or more settings according to a template.
+	 *
+	 * @see PHP class WP_Customize_Partial.
+	 *
+	 * @class
+	 * @augments wp.customize.Class
+	 * @since 4.5.0
+	 *
+	 * @param {string} id                              Unique identifier for the control instance.
+	 * @param {object} options                         Options hash for the control instance.
+	 * @param {object} options.params
+	 * @param {string} options.params.type             Type of partial (e.g. nav_menu, widget, etc)
+	 * @param {string} options.params.selector         jQuery selector to find the container element in the page.
+	 * @param {array}  options.params.settings         The IDs for the settings the partial relates to.
+	 * @param {string} options.params.primarySetting   The ID for the primary setting the partial renders.
+	 * @param {bool}   options.params.fallbackRefresh  Whether to refresh the entire preview in case of a partial refresh failure.
+	 */
+	Partial = self.Partial = api.Class.extend({
+
+		id: null,
+
+		 /**
+		 * Constructor.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param {string} id - Partial ID.
+		 * @param {Object} options
+		 * @param {Object} options.params
+		 */
+		initialize: function( id, options ) {
+			var partial = this;
+			options = options || {};
+			partial.id = id;
+
+			partial.params = _.extend(
+				{
+					selector: null,
+					settings: [],
+					primarySetting: null,
+					containerInclusive: false,
+					fallbackRefresh: true // Note this needs to be false in a front-end editing context.
+				},
+				options.params || {}
+			);
+
+			partial.deferred = {};
+			partial.deferred.ready = $.Deferred();
+
+			partial.deferred.ready.done( function() {
+				partial.ready();
+			} );
+		},
+
+		/**
+		 * Set up the partial.
+		 *
+		 * @since 4.5.0
+		 */
+		ready: function() {
+			var partial = this;
+			_.each( _.pluck( partial.placements(), 'container' ), function( container ) {
+				$( container ).attr( 'title', self.data.l10n.shiftClickToEdit );
+			} );
+			$( document ).on( 'click', partial.params.selector, function( e ) {
+				if ( ! e.shiftKey ) {
+					return;
+				}
+				e.preventDefault();
+				_.each( partial.placements(), function( placement ) {
+					if ( $( placement.container ).is( e.currentTarget ) ) {
+						partial.showControl();
+					}
+				} );
+			} );
+		},
+
+		/**
+		 * Find all placements for this partial int he document.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @return {Array.<Placement>}
+		 */
+		placements: function() {
+			var partial = this, selector;
+
+			selector = partial.params.selector || '';
+			if ( selector ) {
+				selector += ', ';
+			}
+			selector += '[data-customize-partial-id="' + partial.id + '"]'; // @todo Consider injecting customize-partial-id-${id} classnames instead.
+
+			return $( selector ).map( function() {
+				var container = $( this ), context;
+
+				context = container.data( 'customize-partial-placement-context' );
+				if ( _.isString( context ) && '{' === context.substr( 0, 1 ) ) {
+					throw new Error( 'context JSON parse error' );
+				}
+
+				return new Placement( {
+					partial: partial,
+					container: container,
+					context: context
+				} );
+			} ).get();
+		},
+
+		/**
+		 * Get list of setting IDs related to this partial.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @return {String[]}
+		 */
+		settings: function() {
+			var partial = this;
+			if ( partial.params.settings && 0 !== partial.params.settings.length ) {
+				return partial.params.settings;
+			} else if ( partial.params.primarySetting ) {
+				return [ partial.params.primarySetting ];
+			} else {
+				return [ partial.id ];
+			}
+		},
+
+		/**
+		 * Return whether the setting is related to the partial.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param {wp.customize.Value|string} setting  ID or object for setting.
+		 * @return {boolean} Whether the setting is related to the partial.
+		 */
+		isRelatedSetting: function( setting /*... newValue, oldValue */ ) {
+			var partial = this;
+			if ( _.isString( setting ) ) {
+				setting = api( setting );
+			}
+			if ( ! setting ) {
+				return false;
+			}
+			return -1 !== _.indexOf( partial.settings(), setting.id );
+		},
+
+		/**
+		 * Show the control to modify this partial's setting(s).
+		 *
+		 * This may be overridden for inline editing.
+		 *
+		 * @since 4.5.0
+		 */
+		showControl: function() {
+			var partial = this, settingId = partial.params.primarySetting;
+			if ( ! settingId ) {
+				settingId = _.first( partial.settings() );
+			}
+			api.preview.send( 'focus-control-for-setting', settingId );
+		},
+
+		/**
+		 * Prepare container for selective refresh.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param {Placement} placement
+		 */
+		preparePlacement: function( placement ) {
+			$( placement.container ).addClass( 'customize-partial-refreshing' );
+		},
+
+		/**
+		 * Reference to the pending promise returned from self.requestPartial().
+		 *
+		 * @since 4.5.0
+		 * @private
+		 */
+		_pendingRefreshPromise: null,
+
+		/**
+		 * Request the new partial and render it into the placements.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @this {wp.customize.selectiveRefresh.Partial}
+		 * @return {jQuery.Promise}
+		 */
+		refresh: function() {
+			var partial = this, refreshPromise;
+
+			refreshPromise = self.requestPartial( partial );
+
+			if ( ! partial._pendingRefreshPromise ) {
+				_.each( partial.placements(), function( placement ) {
+					partial.preparePlacement( placement );
+				} );
+
+				refreshPromise.done( function( placements ) {
+					_.each( placements, function( placement ) {
+						partial.renderContent( placement );
+					} );
+				} );
+
+				refreshPromise.fail( function( data, placements ) {
+					partial.fallback( data, placements );
+				} );
+
+				// Allow new request when this one finishes.
+				partial._pendingRefreshPromise = refreshPromise;
+				refreshPromise.always( function() {
+					partial._pendingRefreshPromise = null;
+				} );
+			}
+
+			return refreshPromise;
+		},
+
+		/**
+		 * Apply the addedContent in the placement to the document.
+		 *
+		 * Note the placement object will have its container and removedNodes
+		 * properties updated.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param {Placement}             placement
+		 * @param {Element|jQuery}        [placement.container]  - This param will be empty if there was no element matching the selector.
+		 * @param {string|object|boolean} placement.addedContent - Rendered HTML content, a data object for JS templates to render, or false if no render.
+		 * @param {object}                [placement.context]    - Optional context information about the container.
+		 * @returns {boolean} Whether the rendering was successful and the fallback was not invoked.
+		 */
+		renderContent: function( placement ) {
+			var partial = this, content, newContainerElement;
+			if ( ! placement.container ) {
+				partial.fallback( new Error( 'no_container' ), [ placement ] );
+				return false;
+			}
+			placement.container = $( placement.container );
+			if ( false === placement.addedContent ) {
+				partial.fallback( new Error( 'missing_render' ), [ placement ] );
+				return false;
+			}
+
+			// Currently a subclass needs to override renderContent to handle partials returning data object.
+			if ( ! _.isString( placement.addedContent ) ) {
+				partial.fallback( new Error( 'non_string_content' ), [ placement ] );
+				return false;
+			}
+
+			/* jshint ignore:start */
+			self.orginalDocumentWrite = document.write;
+			document.write = function() {
+				throw new Error( self.data.l10n.badDocumentWrite );
+			};
+			/* jshint ignore:end */
+			try {
+				content = placement.addedContent;
+				if ( wp.emoji && wp.emoji.parse && ! $.contains( document.head, placement.container[0] ) ) {
+					content = wp.emoji.parse( content );
+				}
+
+				if ( partial.params.containerInclusive ) {
+
+					// Note that content may be an empty string, and in this case jQuery will just remove the oldContainer
+					newContainerElement = $( content );
+
+					// Merge the new context on top of the old context.
+					placement.context = _.extend(
+						placement.context,
+						newContainerElement.data( 'customize-partial-placement-context' ) || {}
+					);
+					newContainerElement.data( 'customize-partial-placement-context', placement.context );
+
+					placement.removedNodes = placement.container;
+					placement.container = newContainerElement;
+					placement.removedNodes.replaceWith( placement.container );
+					placement.container.attr( 'title', self.data.l10n.shiftClickToEdit );
+				} else {
+					placement.removedNodes = document.createDocumentFragment();
+					while ( placement.container[0].firstChild ) {
+						placement.removedNodes.appendChild( placement.container[0].firstChild );
+					}
+
+					placement.container.html( content );
+				}
+
+				placement.container.removeClass( 'customize-render-content-error' );
+			} catch ( error ) {
+				if ( 'undefined' !== typeof console && console.error ) {
+					console.error( partial.id, error );
+				}
+			}
+			/* jshint ignore:start */
+			document.write = self.orginalDocumentWrite;
+			self.orginalDocumentWrite = null;
+			/* jshint ignore:end */
+
+			placement.container.removeClass( 'customize-partial-refreshing' );
+
+			// Prevent placement container from being being re-triggered as being rendered among nested partials.
+			placement.container.data( 'customize-partial-content-rendered', true );
+
+			/**
+			 * Announce when a partial's placement has been rendered so that dynamic elements can be re-built.
+			 */
+			self.trigger( 'partial-content-rendered', placement );
+			return true;
+		},
+
+		/**
+		 * Handle fail to render partial.
+		 *
+		 * The first argument is either the failing jqXHR or an Error object, and the second argument is the array of containers.
+		 *
+		 * @since 4.5.0
+		 */
+		fallback: function() {
+			var partial = this;
+			if ( partial.params.fallbackRefresh ) {
+				self.requestFullRefresh();
+			}
+		}
+	} );
+
+	/**
+	 * A Placement for a Partial.
+	 *
+	 * A partial placement is the actual physical representation of a partial for a given context.
+	 * It also may have information in relation to how a placement may have just changed.
+	 * The placement is conceptually similar to a DOM Range or MutationRecord.
+	 *
+	 * @class
+	 * @augments wp.customize.Class
+	 * @since 4.5.0
+	 */
+	self.Placement = Placement = api.Class.extend({
+
+		/**
+		 * The partial with which the container is associated.
+		 *
+		 * @param {wp.customize.selectiveRefresh.Partial}
+		 */
+		partial: null,
+
+		/**
+		 * DOM element which contains the placement's contents.
+		 *
+		 * This will be null if the startNode and endNode do not point to the same
+		 * DOM element, such as in the case of a sidebar partial.
+		 * This container element itself will be replaced for partials that
+		 * have containerInclusive param defined as true.
+		 */
+		container: null,
+
+		/**
+		 * DOM node for the initial boundary of the placement.
+		 *
+		 * This will normally be the same as endNode since most placements appear as elements.
+		 * This is primarily useful for widget sidebars which do not have intrinsic containers, but
+		 * for which an HTML comment is output before to mark the starting position.
+		 */
+		startNode: null,
+
+		/**
+		 * DOM node for the terminal boundary of the placement.
+		 *
+		 * This will normally be the same as startNode since most placements appear as elements.
+		 * This is primarily useful for widget sidebars which do not have intrinsic containers, but
+		 * for which an HTML comment is output before to mark the ending position.
+		 */
+		endNode: null,
+
+		/**
+		 * Context data.
+		 *
+		 * This provides information about the placement which is included in the request
+		 * in order to render the partial properly.
+		 *
+		 * @param {object}
+		 */
+		context: null,
+
+		/**
+		 * The content for the partial when refreshed.
+		 *
+		 * @param {string}
+		 */
+		addedContent: null,
+
+		/**
+		 * DOM node(s) removed when the partial is refreshed.
+		 *
+		 * If the partial is containerInclusive, then the removedNodes will be
+		 * the single Element that was the partial's former placement. If the
+		 * partial is not containerInclusive, then the removedNodes will be a
+		 * documentFragment containing the nodes removed.
+		 *
+		 * @param {Element|DocumentFragment}
+		 */
+		removedNodes: null,
+
+		/**
+		 * Constructor.
+		 *
+		 * @since 4.5.0
+		 *
+		 * @param {object}                   args
+		 * @param {Partial}                  args.partial
+		 * @param {jQuery|Element}           [args.container]
+		 * @param {Node}                     [args.startNode]
+		 * @param {Node}                     [args.endNode]
+		 * @param {object}                   [args.context]
+		 * @param {string}                   [args.addedContent]
+		 * @param {jQuery|DocumentFragment}  [args.removedNodes]
+		 */
+		initialize: function( args ) {
+			var placement = this;
+
+			args = _.extend( {}, args || {} );
+			if ( ! args.partial || ! args.partial.extended( Partial ) ) {
+				throw new Error( 'Missing partial' );
+			}
+			args.context = args.context || {};
+			if ( args.container ) {
+				args.container = $( args.container );
+			}
+
+			_.extend( placement, args );
+		}
+
+	});
+
+	/**
+	 * Mapping of type names to Partial constructor subclasses.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @type {Object.<string, wp.customize.selectiveRefresh.Partial>}
+	 */
+	self.partialConstructor = {};
+
+	self.partial = new api.Values({ defaultConstructor: Partial });
+
+	/**
+	 * Get the POST vars for a Customizer preview request.
+	 *
+	 * @since 4.5.0
+	 * @see wp.customize.previewer.query()
+	 *
+	 * @return {object}
+	 */
+	self.getCustomizeQuery = function() {
+		var dirtyCustomized = {};
+		api.each( function( value, key ) {
+			if ( value._dirty ) {
+				dirtyCustomized[ key ] = value();
+			}
+		} );
+
+		return {
+			wp_customize: 'on',
+			nonce: api.settings.nonce.preview,
+			theme: api.settings.theme.stylesheet,
+			customized: JSON.stringify( dirtyCustomized )
+		};
+	};
+
+	/**
+	 * Currently-requested partials and their associated deferreds.
+	 *
+	 * @since 4.5.0
+	 * @type {Object<string, { deferred: jQuery.Promise, partial: wp.customize.selectiveRefresh.Partial }>}
+	 */
+	self._pendingPartialRequests = {};
+
+	/**
+	 * Timeout ID for the current requesr, or null if no request is current.
+	 *
+	 * @since 4.5.0
+	 * @type {number|null}
+	 * @private
+	 */
+	self._debouncedTimeoutId = null;
+
+	/**
+	 * Current jqXHR for the request to the partials.
+	 *
+	 * @since 4.5.0
+	 * @type {jQuery.jqXHR|null}
+	 * @private
+	 */
+	self._currentRequest = null;
+
+	/**
+	 * Request full page refresh.
+	 *
+	 * When selective refresh is embedded in the context of front-end editing, this request
+	 * must fail or else changes will be lost, unless transactions are implemented.
+	 *
+	 * @since 4.5.0
+	 */
+	self.requestFullRefresh = function() {
+		api.preview.send( 'refresh' );
+	};
+
+	/**
+	 * Request a re-rendering of a partial.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param {wp.customize.selectiveRefresh.Partial} partial
+	 * @return {jQuery.Promise}
+	 */
+	self.requestPartial = function( partial ) {
+		var partialRequest;
+
+		if ( self._debouncedTimeoutId ) {
+			clearTimeout( self._debouncedTimeoutId );
+			self._debouncedTimeoutId = null;
+		}
+		if ( self._currentRequest ) {
+			self._currentRequest.abort();
+			self._currentRequest = null;
+		}
+
+		partialRequest = self._pendingPartialRequests[ partial.id ];
+		if ( ! partialRequest || 'pending' !== partialRequest.deferred.state() ) {
+			partialRequest = {
+				deferred: $.Deferred(),
+				partial: partial
+			};
+			self._pendingPartialRequests[ partial.id ] = partialRequest;
+		}
+
+		// Prevent leaking partial into debounced timeout callback.
+		partial = null;
+
+		self._debouncedTimeoutId = setTimeout(
+			function() {
+				var data, partialPlacementContexts, partialsPlacements, request;
+
+				self._debouncedTimeoutId = null;
+				data = self.getCustomizeQuery();
+
+				/*
+				 * It is key that the containers be fetched exactly at the point of the request being
+				 * made, because the containers need to be mapped to responses by array indices.
+				 */
+				partialsPlacements = {};
+
+				partialPlacementContexts = {};
+
+				_.each( self._pendingPartialRequests, function( pending, partialId ) {
+					partialsPlacements[ partialId ] = pending.partial.placements();
+					if ( ! self.partial.has( partialId ) ) {
+						pending.deferred.rejectWith( pending.partial, [ new Error( 'partial_removed' ), partialsPlacements[ partialId ] ] );
+					} else {
+						/*
+						 * Note that this may in fact be an empty array. In that case, it is the responsibility
+						 * of the Partial subclass instance to know where to inject the response, or else to
+						 * just issue a refresh (default behavior). The data being returned with each container
+						 * is the context information that may be needed to render certain partials, such as
+						 * the contained sidebar for rendering widgets or what the nav menu args are for a menu.
+						 */
+						partialPlacementContexts[ partialId ] = _.map( partialsPlacements[ partialId ], function( placement ) {
+							return placement.context || {};
+						} );
+					}
+				} );
+
+				data.partials = JSON.stringify( partialPlacementContexts );
+				data[ self.data.renderQueryVar ] = '1';
+
+				request = self._currentRequest = wp.ajax.send( null, {
+					data: data,
+					url: api.settings.url.self
+				} );
+
+				request.done( function( data ) {
+
+					/**
+					 * Announce the data returned from a request to render partials.
+					 *
+					 * The data is filtered on the server via customize_render_partials_response
+					 * so plugins can inject data from the server to be utilized
+					 * on the client via this event. Plugins may use this filter
+					 * to communicate script and style dependencies that need to get
+					 * injected into the page to support the rendered partials.
+					 * This is similar to the 'saved' event.
+					 */
+					self.trigger( 'render-partials-response', data );
+
+					// Relay errors (warnings) captured during rendering and relay to console.
+					if ( data.errors && 'undefined' !== typeof console && console.warn ) {
+						_.each( data.errors, function( error ) {
+							console.warn( error );
+						} );
+					}
+
+					/*
+					 * Note that data is an array of items that correspond to the array of
+					 * containers that were submitted in the request. So we zip up the
+					 * array of containers with the array of contents for those containers,
+					 * and send them into .
+					 */
+					_.each( self._pendingPartialRequests, function( pending, partialId ) {
+						var placementsContents;
+						if ( ! _.isArray( data.contents[ partialId ] ) ) {
+							pending.deferred.rejectWith( pending.partial, [ new Error( 'unrecognized_partial' ), partialsPlacements[ partialId ] ] );
+						} else {
+							placementsContents = _.map( data.contents[ partialId ], function( content, i ) {
+								var partialPlacement = partialsPlacements[ partialId ][ i ];
+								if ( partialPlacement ) {
+									partialPlacement.addedContent = content;
+								} else {
+									partialPlacement = new Placement( {
+										partial: pending.partial,
+										addedContent: content
+									} );
+								}
+								return partialPlacement;
+							} );
+							pending.deferred.resolveWith( pending.partial, [ placementsContents ] );
+						}
+					} );
+					self._pendingPartialRequests = {};
+				} );
+
+				request.fail( function( data, statusText ) {
+
+					/*
+					 * Ignore failures caused by partial.currentRequest.abort()
+					 * The pending deferreds will remain in self._pendingPartialRequests
+					 * for re-use with the next request.
+					 */
+					if ( 'abort' === statusText ) {
+						return;
+					}
+
+					_.each( self._pendingPartialRequests, function( pending, partialId ) {
+						pending.deferred.rejectWith( pending.partial, [ data, partialsPlacements[ partialId ] ] );
+					} );
+					self._pendingPartialRequests = {};
+				} );
+			},
+			self.data.refreshBuffer
+		);
+
+		return partialRequest.deferred.promise();
+	};
+
+	/**
+	 * Add partials for any nav menu container elements in the document.
+	 *
+	 * This method may be called multiple times. Containers that already have been
+	 * seen will be skipped.
+	 *
+	 * @since 4.5.0
+	 *
+	 * @param {jQuery|HTMLElement} [rootElement]
+	 * @param {object}             [options]
+	 * @param {boolean=true}       [options.triggerRendered]
+	 */
+	self.addPartials = function( rootElement, options ) {
+		var containerElements;
+		if ( ! rootElement ) {
+			rootElement = document.documentElement;
+		}
+		rootElement = $( rootElement );
+		options = _.extend(
+			{
+				triggerRendered: true
+			},
+			options || {}
+		);
+
+		containerElements = rootElement.find( '[data-customize-partial-id]' );
+		if ( rootElement.is( '[data-customize-partial-id]' ) ) {
+			containerElements = containerElements.add( rootElement );
+		}
+		containerElements.each( function() {
+			var containerElement = $( this ), partial, id, Constructor, partialOptions, containerContext;
+			id = containerElement.data( 'customize-partial-id' );
+			if ( ! id ) {
+				return;
+			}
+			containerContext = containerElement.data( 'customize-partial-placement-context' ) || {};
+
+			partial = self.partial( id );
+			if ( ! partial ) {
+				partialOptions = containerElement.data( 'customize-partial-options' ) || {};
+				partialOptions.constructingContainerContext = containerElement.data( 'customize-partial-placement-context' ) || {};
+				Constructor = self.partialConstructor[ containerElement.data( 'customize-partial-type' ) ] || self.Partial;
+				partial = new Constructor( id, partialOptions );
+				self.partial.add( partial.id, partial );
+			}
+
+			/*
+			 * Only trigger renders on (nested) partials that have been not been
+			 * handled yet. An example where this would apply is a nav menu
+			 * embedded inside of a custom menu widget. When the widget's title
+			 * is updated, the entire widget will re-render and then the event
+			 * will be triggered for the nested nav menu to do any initialization.
+			 */
+			if ( options.triggerRendered && ! containerElement.data( 'customize-partial-content-rendered' ) ) {
+
+				/**
+				 * Announce when a partial's nested placement has been re-rendered.
+				 */
+				self.trigger( 'partial-content-rendered', new Placement( {
+					partial: partial,
+					context: containerContext,
+					container: containerElement
+				} ) );
+			}
+			containerElement.data( 'customize-partial-content-rendered', true );
+		} );
+	};
+
+	api.bind( 'preview-ready', function() {
+		var handleSettingChange, watchSettingChange, unwatchSettingChange;
+
+		// Polyfill for IE8 to support the document.head attribute.
+		if ( ! document.head ) {
+			document.head = $( 'head:first' )[0];
+		}
+
+		_.extend( self.data, _customizePartialRefreshExports );
+
+		// Create the partial JS models.
+		_.each( self.data.partials, function( data, id ) {
+			var Constructor, partial = self.partial( id );
+			if ( ! partial ) {
+				Constructor = self.partialConstructor[ data.type ] || self.Partial;
+				partial = new Constructor( id, { params: data } );
+				self.partial.add( id, partial );
+			} else {
+				_.extend( partial.params, data );
+			}
+		} );
+
+		/**
+		 * Handle change to a setting.
+		 *
+		 * Note this is largely needed because adding a 'change' event handler to wp.customize
+		 * will only include the changed setting object as an argument, not including the
+		 * new value or the old value.
+		 *
+		 * @since 4.5.0
+		 * @this {wp.customize.Setting}
+		 *
+		 * @param {*|null} newValue New value, or null if the setting was just removed.
+		 * @param {*|null} oldValue Old value, or null if the setting was just added.
+		 */
+		handleSettingChange = function( newValue, oldValue ) {
+			var setting = this;
+			self.partial.each( function( partial ) {
+				if ( partial.isRelatedSetting( setting, newValue, oldValue ) ) {
+					partial.refresh();
+				}
+			} );
+		};
+
+		/**
+		 * Trigger the initial change for the added setting, and watch for changes.
+		 *
+		 * @since 4.5.0
+		 * @this {wp.customize.Values}
+		 *
+		 * @param {wp.customize.Setting} setting
+		 */
+		watchSettingChange = function( setting ) {
+			handleSettingChange.call( setting, setting(), null );
+			setting.bind( handleSettingChange );
+		};
+
+		/**
+		 * Trigger the final change for the removed setting, and unwatch for changes.
+		 *
+		 * @since 4.5.0
+		 * @this {wp.customize.Values}
+		 *
+		 * @param {wp.customize.Setting} setting
+		 */
+		unwatchSettingChange = function( setting ) {
+			handleSettingChange.call( setting, null, setting() );
+			setting.unbind( handleSettingChange );
+		};
+
+		api.bind( 'add', watchSettingChange );
+		api.bind( 'remove', unwatchSettingChange );
+		api.each( function( setting ) {
+			setting.bind( handleSettingChange );
+		} );
+
+		// Add (dynamic) initial partials that are declared via data-* attributes.
+		self.addPartials( document.documentElement, {
+			triggerRendered: false
+		} );
+
+		// Add new dynamic partials when the document changes.
+		if ( 'undefined' !== typeof MutationObserver ) {
+			self.mutationObserver = new MutationObserver( function( mutations ) {
+				_.each( mutations, function( mutation ) {
+					self.addPartials( $( mutation.target ) );
+				} );
+			} );
+			self.mutationObserver.observe( document.documentElement, {
+				childList: true,
+				subtree: true
+			} );
+		}
+
+		/**
+		 * Handle rendering of partials.
+		 *
+		 * @param {api.selectiveRefresh.Placement} placement
+		 */
+		api.selectiveRefresh.bind( 'partial-content-rendered', function( placement ) {
+			if ( placement.container ) {
+				self.addPartials( placement.container );
+			}
+		} );
+
+		api.preview.bind( 'active', function() {
+
+			// Make all partials ready.
+			self.partial.each( function( partial ) {
+				partial.deferred.ready.resolve();
+			} );
+
+			// Make all partials added henceforth as ready upon add.
+			self.partial.bind( 'add', function( partial ) {
+				partial.deferred.ready.resolve();
+			} );
+		} );
+
+	} );
+
+	return self;
+}( jQuery, wp.customize ) );