Zod Custom Events

Type safe, framework agnostic, Zod based, custom events extension library.

• ✅ Utilize the full controll of CustomEvents with a custom API
• ✅ End-to-end type safety; validate event payload at runtime via your provided Zod schema
• ✅ Framework agnostic; runs on any JavaScript environment
• ✅ Supports all CustomEvent native properties and methods inherited by the Event interface
• ✅ Middleware support for event processing
• ✅ Less than 1kb minified and gzipped

Table of Contents

• Installation
  • Prerequisites
  • Using NPM
  • Using JSR
  • Using a CDN
• Usage
• API Reference
  • EventController
• Contributing
• License

Preview

Installation

Prerequisites

• Zod

Install zod-custom-events using your favorite package manager or CDN, then include it in your project:

Using NPM

# Install with npm
npm install zod-custom-events

# Install with pnpm
pnpm add zod-custom-events

# Install with yarn
yarn add zod-custom-events

# Install with bun
bun add zod-custom-events

Using JSR

# Install in a node project
npx jsr add @georgecht/zod-custom-events

# Install in a deno project
deno add jsr:@georgecht/zod-custom-events

# Install in a bun project
bunx jsr add @georgecht/zod-custom-events

Using a CDN

<!-- Via jsdelivr -->
<script src="https://cdn.jsdelivr.net/npm/zod-custom-events@latest/dist/index.min.js"></script>

<!-- Via unpkg -->
<script src="https://www.unpkg.com/zod-custom-events/dist/index.min.js"></script>

Usage

Here's a basic example of how to use zod-custom-events:

import { z } from 'zod';
import { EventController } from 'zod-custom-events';

// Define your event schema
const userSchema = z.object({
  id: z.number(),
  email: z.email(),
});

// Create an event controller
const userEventController = new EventController(userSchema, 'user-event');

// Subscribe to the event
userEventController.subscribe((event) => {
  console.log('Received user event:', event.detail);
});

// Dispatch an event
userEventController.dispatch({
  id: 123,
  email: 'my@email.com',
});

// Cleanup
userEventController.unsubscribe();

API Reference

The API reference is available on GitHub.

EventController

The main class for managing custom events. The EventController<T extends ZodSchema> extends the CustomEvent interface with a detail property of type T. Meaning it will match the CustomEvent interface and infer all the functionality.

---

👉 Constructor

constructor(schema: T, eventName: string, options?: EventControllerOptions<T>)

Creates a new EventController instance.

Parameters

• schema - The Zod schema for validating the event payload.
• eventName - The name of the custom event.
• options optional - Configuration options for the EventController.

Example

import { z } from 'zod';
import { EventController } from 'zod-custom-events';

const schema = z.object({
  name: z.string(),
});

const controller = new EventController(schema, 'myEvent', {
  onError: ({ error }) => console.error('Validation error:', error),
  onDispatch: ({ payload }) => console.log('Dispatching event with payload:', payload),
});

Available options

• element optional - The element to bind the event to. Defaults to window.
• onError optional - Error handler for validation errors.
• onDispatch optional - Callback function called before dispatching the event.
• onSubscribe optional - Callback function called when the event listener is added.
• onUnsubscribe optional - Callback function called when the event listener is removed.

---

👉 Subscribe

Subscribe to the event.

subscribe(listener: (event: TypedCustomEvent<EventPayload<T>>) => void, options?: AddEventListenerOptions): void

Parameters

• listener - The function to be called when the event is triggered.
• options - Optional parameters for the event listener.

Available options

• once optional - A boolean value indicating that the listener should be invoked at most once after being added. If true, the listener would be automatically removed when invoked.
• passive optional - A boolean indicating whether the event listener is a passive listener. If set to true, indicates that the function specified by listener will never call preventDefault(). If a passive listener calls preventDefault(), nothing will happen and a console warning may be generated.
• signal optional - An AbortSignal to signal when the listener should be removed.

Simple example

controller.subscribe((event) => {
  console.log('Received user event:', event.detail);
});

Example with abort signal and once option

// With abort signal and once option
const abortController = new AbortController();
const { signal } = abortController;

controller.subscribe((event) => {
  console.log('Received user event:', event.detail);
}, { signal, once: true });

// Later in the code
abortController.abort();

---

👉 Unsubscribe

Removes the previously registered event listener for the event.

unsubscribe(options?: EventListenerOptions): void

Parameters

• options optional - Optional parameters to match the event listener.

Available options

• capture optional - A boolean value indicating that events of this type will be dispatched to the registered listener before being dispatched to any EventTarget beneath it in the DOM tree.

Example

controller.unsubscribe();

---

👉 Dispatch

Dispatches the event, validating its payload using the Zod schema and applying middleware.

dispatch(payload: EventPayload<T>, eventInitDict?: CustomEventInit<EventPayload<T>>): Promise<void>

Parameters

• payload - The data associated with the event. Validated against the Zod schema initially provided.
• eventInitDict optional - Optional parameters for initializing the event.

Available eventInitDict options

• bubbles optional - A boolean value indicating whether or not the event can bubble through the DOM.
• cancelable optional - A boolean value indicating whether the event can be cancelled.
• composed optional - A boolean value indicating whether the event will trigger listeners outside of a shadow root (see Event.composed for more details).

Example

controller.dispatch({
  id: 1,
  name: 'John Doe',
}, {
  bubbles: true
});

---

👉 Refine

Sets a condition for the event, allowing control over whether the event is dispatched.

refine(condition: (payload: EventPayload<T>) => boolean, callback?: (ctx: EventPayloadContext<T>) => void): void

Parameters

• condition - A function that takes the event payload as input and returns a boolean.
• callback optional - An optional callback function to be called when the condition is not met.

Example

controller.refine(
  (payload) => payload.id > 0,
  (ctx) => {
    const { payload } = ctx;
    console.log("Invalid user ID:", payload.id)
  }
);

---

👉 Update

Updates the EventController options.

update(options: Partial<EventControllerOptions<T>>): void

Parameters

• options optional - New configuration options for the EventController.

Example

const controller = new EventController(schema, 'myEvent');

// Later in the code
controller.update({
  onError: ({ error }) => console.warn('New error handler:', error),
  onDispatch: ({ payload }) => console.log('New dispatch handler:', payload),
});

---

👉 Use

Adds a middleware function to the event processing pipeline.

use(middleware: Middleware<EventPayload<T>>): void

Parameters

• middleware - A function that processes the event context and calls the next middleware.

Example

controller.use(async (ctx, next) => {
  console.log("Processing user event:", ctx.payload);
  await next();
});

Contributing

Contributions are welcome! Please open an issue or submit a pull request.

License

This project is licensed under the MIT License. See the LICENSE file for more details.