EventBus

EventBus is a simple event management library for TypeScript.

Installation

npm install @ai-zen/event-bus

Usage

import EventBus from "@ai-zen/event-bus";

// Create a new instance of EventBus
const eventBus = new EventBus();

// Subscribe to an event
eventBus.on("eventName", (arg1, arg2) => {
  // Handle the event
});

// Unsubscribe from an event
eventBus.off("eventName", handler);

// Unsubscribe from all handlers of an event
eventBus.offAll("eventName");

// Destroy the event bus and remove all event subscriptions
eventBus.destroy();

// Emit an event
eventBus.emit("eventName", arg1, arg2);

// Gather the results returned by all handlers of an event
const results = eventBus.gather < T > ("eventName", arg1, arg2);

// Gather the results returned by all handlers of an event as a map
const resultsMap = eventBus.gatherMap < T > ("eventName", arg1, arg2);

// Subscribe to an event and automatically unsubscribe after the first invocation
eventBus.once("eventName", (arg1, arg2) => {
  // Handle the event
});

// Subscribe to an event and return a promise that resolves when the event is emitted
const resultPromise = eventBus.promise("eventName");

API

on(name: string, handler: EventHandler, error?: ErrorHandler): Disposable

Subscribes to an event.

• name (required): The name of the event to subscribe to.
• handler (required): The event handler function.
• error (optional): The error handler function.
• Returns: A Disposable object that can be used to unsubscribe from the event.

Example

const disposable = eventBus.on("eventName", (arg1, arg2) => {
  // Handle the event
});

// Unsubscribe from the event
disposable.dispose();

off(name: string, handler: EventHandler): boolean

Unsubscribes from an event.

• name (required): The name of the event to unsubscribe from.
• handler (required): The event handler function.
• Returns: True if the unsubscribing was successful, otherwise false.

offAll(name: string): void

Unsubscribes all event handlers from an event.

• name (required): The name of the event to unsubscribe all handlers from.

destroy(): void

Destroys the event bus by clearing all event subscribers.

emit(name: string, ...args: any[]): void

Emits an event.

• name (required): The name of the event to emit.
• args (optional): The arguments to pass to the event handlers.

error(name: string, reason: any): void

This method is used to send an error event through the event bus.

• name (required): The name of the error event to be sent.
• reason (required): The reason for the error.

Example

try {
  // Do something that might throw an error
  const data = await getData();
  eventBus.emit("fooEvent", data);
} catch (error) {
  eventBus.error("fooEvent", error); // Send an error event
}

// Use the error handler function for eventBus.on
eventBus.on(
  "fooEvent",
  (data) => {
    // Handle the data
  },
  (error) => {
    // Handle the error
  }
);

// You can also use a promise catch to handle the error
eventBus.promise("fooEvent").catch((error) => {
  // Handle the error
});

gather<T>(name: string, ...args: any[]): T[]

Gathers the results from all event handlers of the specified event.

• name (required): The name of the event to gather results from.
• args (optional): The arguments to pass to the event handlers.
• Returns: An array of results from all event handlers.

gatherMap<T>(name: string, ...args: any[]): Map<EventHandler, T>

Gathers the results from all event handlers of the specified event with a map of the handlers.

• name (required): The name of the event to gather results from.
• args (optional): The arguments to pass to the event handlers.
• Returns: A map of event handlers and their corresponding results.

once(name: string, handler: EventHandler, error?: ErrorHandler): Disposable

Subscribes to an event and unsubscribes automatically after the event is emitted once.

• name (required): The name of the event to subscribe to.
• handler (required): The event handler function.
• error (optional): The error handler function.
• Returns: A Disposable object that can be used to unsubscribe from the event.

Example

const disposable = eventBus.once("eventName", (arg1, arg2) => {
  // Handle the event
});

// The handler will be automatically unsubscribed after the first invocation

promise(name: string): Promise<any>

Returns a promise that resolves when the specified event is emitted.

• name (required): The name of the event to create a promise for.
• Returns: A promise that resolves when the event is emitted.

Example

const resultPromise = eventBus.promise("eventName");

resultPromise.then((result) => {
  // Handle the result
});

subscribe(name: string, handler: EventHandler): void

Alias for the on method.

unsubscribe(name: string, handler: EventHandler): boolean

Alias for the off method.

publish(name: string, ...args: any[]): void

Alias for the emit method.

License

MIT