Events & Hooks

bknd comes with a powerful built-in event system that allows you to hook into the app lifecycle and extend its functionality. You can hook into these events in two ways:

• async: Your listener is not blocking the main execution flow. E.g. on Cloudflare Workers, by default, the ExecutionContext’s waitUntil method is used so that the listeners runs after the response is sent.
• sync: Your listener is blocking the main execution flow. This allows to abort the request in your custom conditions. Some events also allow to return a modified event payload.

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Overview

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Listening to events

You can listen to events by using the EventManager exposed at app.emgr. To register a listener, you can use either of these methods:

• onEvent: Register a listener for a specific event with a typed event.
• on: Register a listener for an event by its slug.
• onAny: Register a listener for all events.

import { createApp, AppEvents } from "bknd";
const app = createApp();

app.emgr.onEvent(AppEvents.AppRequest, async (event) => {
   //                                         ^? AppRequest
   console.log("Request received", event.request.url);
});

app.emgr.on("app-request", async (event) => {
   console.log("Request received", event.request.url);
});

app.emgr.onAny(async (event) => {
   console.log("Event received", event.slug);
});

You may want to register your listeners inside bknd.config.ts to make sure they are registered before the app is built:

import { AppEvents } from "bknd";

export default {
   onBuilt: (app) => {
      app.emgr.onEvent(AppEvents.AppRequest, async (event) => {
         console.log("Request received", event.request.url);
      });
   }
}

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Setting a mode

By default, listeners are registered as async listeners, meaning that the listener is not blocking the main execution flow. You can change this by passing the mode as the third argument:

app.emgr.onEvent(AppEvents.AppRequest, async (event) => {
   console.log("Request received", event.request.url);
}, { mode: "sync" });

This works for all three methods.

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App Events

These events are emitted by the App class and are available on the AppEvents object.

import { AppEvents } from "bknd";

Available events:

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Database Events

These events are emitted by the Database class and are available on the DatabaseEvents object. These are divided by events triggered by the Mutator and Repository classes.

import { DatabaseEvents } from "bknd/data";

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Mutator Events

These events are emitted during database mutations (insert, update, delete operations).

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Repository Events

These events are emitted during database queries (find operations).

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Media Events

These events are emitted by the Storage class and are available on the MediaEvents object.

import { MediaEvents } from "bknd/media";

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Auth Events

Coming soon.