Class EventEmitter

An abstract class for creating event emitters

Type parameters

<EventMap extends EventNamesMap>

type EventNamesMap = Record<string, string>;

Properties

EVENT_NAMES

A map of valid event names

• Type: EventNamesMap
• Default: {}

Methods

on(eventName, callback)

Add event listener for an event

Type parameters

• <Key extends keyof EventMap>

Parameters

• eventName
  • Type: Key
• callback
  • Type: (data: unknown) => void

off(eventName, callback)

Remove event listener for an event

Type parameters

• <Key extends keyof EventMap>

Parameters

• eventName
  • Type: Key
• callback
  • Type: (data: unknown) => void

emit(eventName, data)

Dispatch event

Type parameters

• <Key extends keyof EventMap>

Parameters

• eventName
  • Type: Key
• data
  • Type: unknown | undefined

Example

Here is a class called Stream that sends events when the stream starts, stops and when the stream receives input. Any event listener listening to the "new" event, will receive the input from the stream.

import { EventEmitter } from "@prozilla-os/shared";

const StreamEvents = {
	new: "new",
	start: "start",
	stop: "stop",
} as const;

export class Stream extends EventEmitter<typeof StreamEvents> {
	static EVENT_NAMES = StreamEvents;

	enabled: boolean = false;

	start() {
		if (this.enabled)
			return;

		this.enabled = true;
		this.emit("start");
	}

	stop() {
		if (!this.enabled)
			return;

		this.enabled = false;
		this.emit("stop");
	}

	send(text: string) {
		if (this.enabled)
			this.emit("new", text);
	}
}