tseep

Because there are N fastest event emitters. And we are fastest (November 2024) 😏.

Up to x12 faster than eventemitter3 in terms of "classic api event emitters" (currently fastest for not classic too).

---

• Fully typed args of emit method based on events map
• Fully implements NodeJS.EventEmitter type & standart, provides interface
• Worlds fastest pure-js EventEmitter
• Fully tested with eventemitter3 tests
• No external deps
• Only 381 bytes size in real app (brotlied)
• No eval implemented

how it works

Benchmarks

emit-multiple-listeners:

tseep               89,030,882 ops/sec
tseep no-eval       15,235,353 ops/sec
emitix              6,201,874 ops/sec
fastemitter         5,981,406 ops/sec
EventEmitter3       5,698,255 ops/sec
tsee                5,163,550 ops/sec
EventEmitter2       4,588,433 ops/sec
EventEmitter1       4,437,743 ops/sec
mitt                3,587,734 ops/sec
event-emitter       3,508,490 ops/sec
contra/emitter      2,183,943 ops/sec

Fastest is [ 'tseep' ]

benchmarks

Make an issue to include yours event emitter, lets find the fastest!

Install & use

npm i tseep

Simple usage:

import { EventEmitter } from "tseep";

const events = new EventEmitter<{
    foo: (a: number, b: string) => void;
}>();

// foo's arguments is fully type checked
events.emit("foo", 123, "hello world");

Use no-eval version

There is no user code evaluated so its complete safe to use with-eval version.
But in some cases (eg chrome's extensions), you just cant use it.
For this cases there is no-eval version:

import { EventEmitter } from "tseep/lib/ee-safe"; // no-eval version
import { EventEmitter } from "tseep/lib/fallback"; // or with autofallback

// same api

"tseep/lib/fallback" may bundle both versions which may result in bigger app bundle size.
Fun fact: brotlied bundled fallback version is less in size than just ee

Known issues

proto event name

!! __proto__ event name is restricted (type guard exists) !!

context binding

By default listeners are not bound to EventEmitter, so you may get some problems around inheritance.
First of all, better use incapsulation. Its faster, safer, clear.
Other variant is to use addListenerBound/removeListenerBound.
Its 2-3x slower for add/remove operation but than you will have proper 'this' context inside listener.

args length

tseep tries to evade spread operator and pass arguments directly.
It will always pass at least 5 arguments, filling non existing args as undefined.
So if you use spread operator inside listener for arguments, you may have more args than you passed.
It's a tradeoff for optimization.

Better use 5 or less arguments for listener, because js engine will optimize it and pass directly through registers.
(actually 6 arguments, but 1 argument is used as event name)

Api

EventEmitter<T> where T extends { [eventName]: Call signature }.

EventEmitter.emit's args is fully typed based on events map.

// Listener = (...args: any[]) => Promise<any>|void
// EventMap extends { [event in (string|symbol)]: Listener }

class EventEmitter<EventMap> {
    readonly maxListeners: number;
    readonly _eventsCount: number;

    emit(event: EventKey, ...args: ArgsN<EventMap[EventKey]>): boolean;
    on(event: EventKey, listener: EventMap[EventKey]): this;
    once(event: EventKey, listener: EventMap[EventKey]): this;
    addListener(event: EventKey, listener: EventMap[EventKey], argsNum?: ArgsNum<EventMap[EventKey]>): this;
    removeListener(event: EventKey, listener: EventMap[EventKey]): this;
    hasListeners(event: EventKey): boolean;
    prependListener(event: EventKey, listener: EventMap[EventKey]): this;
    prependOnceListener(event: EventKey, listener: EventMap[EventKey]): this;
    off(event: EventKey, listener: EventMap[EventKey]): this;
    removeAllListeners(event?: EventKey): this;
    setMaxListeners(n: number): this;
    getMaxListeners(): number;
    listeners(event: EventKey): EventMap[EventKey][];
    rawListeners(event: EventKey): EventMap[EventKey][];
    eventNames(): Array<string | symbol>;
    listenerCount(type: EventKey): number;

    // special methods that are a bit slower than addListener/removeListener
    // but they binds listeners to current EventEmitter or custom object
    addListenerBound(event: EventKey, listener: EventMap[EventKey], bindTo?: any = this, argsNum?: ArgsNum<EventMap[EventKey]>): this;
    removeListenerBound(event: EventKey, listener: EventMap[EventKey]): this;
}

Support this project

Boosty

License

MIT