Light-event-emitter NPM

LightEventEmitter

LightEventEmitter is a simplified version Angular's default EventEmitter class that is used for all Output() bindings. It removes some of EventEmitter's functionality that isn't necessary in 99.9% of use-cases in exchange for performance.

LightEventEmitter is a drop-in replacement for EventEmitter.

Instalation

npm i light-event-emitter

Usage

Just use it instead of EventEmitter.

import { LightEventEmitter } from 'light-event-emitter';

@Component({
  selector: 'my-component',
  template: `...`,
})
export class MyComponent {

  @Output() out = new LightEventEmitter();
  
  ...
  
}

How it works

Purpose of this project is also to test performance impact of creating components with 1, 5 and 10 output bindings (@Output) using the default EventEmitter class and LightEventEmitter.

From the results bellow it's obvious that the number of subscriptions a component has does have performance impact.

Angular's EventEmitter class inherits from RxJS's Subject which means it does a lot of overhead work that is almost never necessary. In particular RxJS Subjects support error and complete notifications that are never useful when sending events via @Output. This means that Subjects have to maintain and check their internal state on every new subscription and even more importantly on every next() emission. However, in typical use-cases with @Output this is never necessary and thus we could be using @Output with some other object than EventEmitter without all this unnecessary functionality that could perform much better.

LightEventEmitter is stripped of its internal state which makes subscriptions faster and emitting values even faster. For this reason it doesn't support error and complete notifications.