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0.56.1 • Public • Published

Snap Controller

NPM Status

The heart of controlling Search, Autocomplete, & Finder functionality. The Controller is responsible for tying various Snap services together.


Snap Controller is a top-level package that requires the following dependencies as services:

NPM Status @searchspring/snap-client

NPM Status @searchspring/snap-store-mobx

NPM Status @searchspring/snap-url-manager

NPM Status @searchspring/snap-event-manager

NPM Status @searchspring/snap-profiler

NPM Status @searchspring/snap-logger


To install the snap-controller package and it's services:

npm install --save @searchspring/snap-controller @searchspring/snap-client @searchspring/snap-store-mobx @searchspring/snap-url-manager @searchspring/snap-event-manager @searchspring/snap-profiler @searchspring/snap-logger


Each Controller must be passed a configuration object as the first parameter to the constructor, and a services object (dependencies) as the second. The contents of these objects will depend on which type of Controller is being instantiated. For example, a SearchController would usually be paired with a SearchStore service, and would take a SearchControllerConfig configuration object.

The complete example below shows how a SearchController could be instatiated, initialized and searched:

import { Client } from '@searchspring/snap-client';
import { SearchStore } from '@searchspring/snap-store-mobx';
import { UrlManager, UrlTranslator } from '@searchspring/snap-url-manager';
import { EventManager } from '@searchspring/snap-event-manager';
import { Profiler } from '@searchspring/snap-profiler';
import { Logger } from '@searchspring/snap-logger';
import { Tracker } from '@searchspring/snap-tracker';
import { SearchController } from '@searchspring/snap-controller';

const configuration = {
	id: 'search'

const urlManager = new UrlManager(new UrlTranslator());
const services = {
	client: new Client({ siteId: 'abc123' }),
	store: new SearchStore(configuration, { urlManager }),
	eventManager: new EventManager(),
	profiler: new Profiler(),
	logger: new Logger(),
	tracker: new Tracker(),

const controller = new SearchController(configuration, services);


The configuration object provided during instantiation provides a way of configuring the controller for different behavior. Each controller type (SearchController, AutocompleteController, FinderController, etc...) has default configurations that can be modified with the instantiation configuration object. At minimum an id attribute is required for identifying controllers. The id should be unique to each instance of a controller.


Along with a configuration, each controller is passed a collection of services during instantiation. These services are then used by the controller and made available via controller methods. Sometimes controllers might share a reference to a service (the client service for example), but in most cases a controller will have it's own instance of a service. Some services (like the SearchStore) share services with the controller (in the example above, the UrlManager is shared).

{ client, store, urlManager, eventManager, profiler, logger }


The client service makes the requests to the API when the controller search method is called. The response is passed onto the store service. This service is exposed as controller.client.


This service mutates the API responses and adds convenience functions for common functionality. The store data is then used by the UI components for display. This service is exposed as controller.store.


urlManager is responsible for updating the page URL when interacting with UI components. The type of translator passed into the UrlManager constructor will determine the types of URLs generated. This service is exposed as controller.urlManager.


Middleware provide an opportunity to hook into these events they occur. Middleware are attached to events, and these events are managed by the eventManager. This service is exposed as controller.eventManager.


Controllers may need to know how long a certain event took, the profiler service provides the means to track this information. This service is exposed as controller.profiler.


The logger service provides logging functionality to a controller. Each controller logs when errors in middleware and when controller events occur. The logger is responsible for sending this information to the developer console. In addition the logger may provide additional emoji or colors to use. This service is exposed as controller.log.


Each Controller can optionally take a 3rd parameter for Context. This is to allow each individual controller to have its own individual context if so desired.

The context is exposed as controller.context



Invoking the init method is required to subscribe to changes that occur in the UrlManager. It also fires the init event which executes attached middleware. This can be fired manually as needed; if it was not manually fired it will happen automatically on the first call to the controller search method.



The search method of a controller will run the search that is expected by leveraging the client service to make the request; the subsequent response will be passed to the store service.

Most controllers will provide a means of manipulating the request and response using beforeSearch and afterSearch events respectively. Read on for details about events.



Different controller types will utilize different Snap Stores (typically of the same name). Each store will provide different properties and methods for its unique purposes. See the documentation for more details.


Each controller will fire various events. Some of the event names are shared between controllers for consistency (ex: beforeSearch, afterSearch, afterStore); however the attaching of middleware and execution of it must remain separate. This is why a new EventManager instance is created for each controller. Middleware are attached to events via the on method and the functions should almost always end with await next() unless purposefully preventing the next attached middleware from executing.

controller.on('init', async (eventData, next) => {
	const { controller } = eventData;

	controller.log.debug('init event has occurred');

	await next();

Note: Groups of middleware (plugins) can be attached using the plugin method.

The data available within a middleware (first parameter) is determined by what gets passed into the fire method. For existing events on the controller, the fire method is already being called when appropriate to the event, and the eventData will typically be an object containing a reference to the controller and any other details that may be of importance to the particular event. Custom events can be created as needed; but keep in mind that any middleware tied to the event should be bound (using on or plugin) prior to the execution of the fire method.

controller.eventManager.fire('customEventName', { thing1: 'one', thing2: 2 });

See the EventManager documentation for more details.


A controller's environment is initialized at build time, and is used to control certain runtime behavior. For example, a production build will supress most logs while a development build will show them all.


The logger provides a clear way of outputting details like profile data or errors to the developer console. A production build will supress most logs while a development build will show them all. The environment is automatically determined, but can be toggled during runtime by setting it to either development or production.

controller.environment = 'development';

The use of console.log() is discouraged. Logging should be done via controller instance to help debug and navigate the sea of console logs. Each controller will output the id for easily deciphering which controller made the log.

controller.log.warn('THIS IS A WARNING!');

Many logs are supressed depending on a development environment of the controller instance. The Logger documentation provides more details about the various methods, colors and emoji available.

Controller Types

Each Controller has a unique configuration and set of default events; it may also provide additional methods for specific functionality.


The base class for all controllers.


Used for autocomplete searches.


A specialized controller used for building custom product finders.


The standard controller used for recommendation profiles.


The standard controller used on search pages and PLPs.




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npm i @searchspring/snap-controller

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