Using Event Hooks

Stencil themes provide access to remote resources through data tags and event hooks. Developers can use these hooks to trigger defined events. A theme can hook to an event to perform actions or calculations based on shopper behavior.

Stencil themes incorporate event hooks by importing the stencil-utils module. Looking at cornerstone/assets/js/theme/, you will see the import statement 'import utils from '@bigcommerce/stencil-utils'; at the top of files using leveraging event hooks.

Cookie Notification Example

In the example below, the cookie-privacy-notification hook enables customization of the alert window that displays European Union–required cookie notifications:

First, ensure you have loaded the stencil-utils package with the following command:

import utils from '@bigcommerce/stencil-utils';

European websites must notify users of cookies to comply with European Union law. The following code implements a hook that will alert shoppers that the website uses cookies.

export default function() {
  // Here you can override the default browser alert box by
  // hooking to the 'cookie-privacy-notification' hook.
  utils.hooks.on('cookie-privacy-notification', (event, privacyMessage) => {
    // You can make your own custom modal or alert box
    // appear in your theme using the privacyMessage provided
    myCustomAlert(privacyMessage);
    // Call event.preventDefault() to prevent the default
    // browser alert from occurring in stencil-utils
    event.preventDefault();
  });
}

A theme would listen for the cookie-privacy-notification event to override the browser’s default notification UI.

Cart Dialog Example

In the following code snippet from Cornerstone in templates/components/products/product-view.html, note the data tag named data‑cart‑item‑add:

<form class="form" method="post" action="{{product.cart_url}}"
    enctype="multipart/form-data" data-cart-item-add>

This data tag enables the emission of the cart‑item‑add event in this next snippet:

/*
 * Import all product-specific js
 */
[...]
import utils from '@bigcommerce/stencil-utils';
[...]
addProductToCart() {
    utils.hooks.on('cart-item-add', (event) => {
        event.preventDefault();
    });
}

Stencil Data Tags and Event Hooks

Stencil themes provide the following chains of data tags, delegated DOM (Document Object Model) events, emitted Stencil event hooks, and Stencil event parameter(s).

Cart Item Added

Hook for items added to the customer’s shopping cart.

itemAdd() {
    this.$body.on('submit', '[data-cart-item-add]', (event) => {
        this.emit('cart-item-add', event, event.target);
    });
}

Faceted-Search Events

Hooks for faceted-search selections that the customer initiates or submits.

searchEvents() {
  this.$body.on('click', '[data-faceted-search-facet]', (event) => {
        this.emit('facetedSearch-facet-clicked', event);
  });
  this.$body.on('submit', '[data-faceted-search-range]', (event) => {
		this.emit('facetedSearch-range-submitted', event);
  });
}