typed-event-emitter-2
This module provides a strict usage and implementation of Node.js' EventEmitter API. Without needing to rely on another implementation. Arbitrary events or listeners can not be added without a TypeScript compile time error.
Install
$ npm i typed-event-emitter-2
Usage
Before using Node.js / Browsers conventional EventEmitter.
import * as UntypedEventEmitter from 'events'; const conventionalEventEmitter = new UntypedEventEmitter(); conventionalEventEmitter .on('foo', (arg: number) => console.log(Math.abs(arg))) .on('bar', (arg: string) => console.log(arg.length)) .on('baz', () => console.log('baz')); conventionalEventEmitter.emit('foo', 1);conventionalEventEmitter.emit('foo'); // Should have an errorconventionalEventEmitter.emit('bar', 'bar');conventionalEventEmitter.emit('bar', 1); // Should have an errorconventionalEventEmitter.emit('baz');conventionalEventEmitter.emit('baz', 'bar'); // Should have an errorUsing a type safe EventEmitter with no arguments in listeners.
import TypedEventEmitter from 'typed-event-emitter-2'; const typedEventEmitterNoArgs = new TypedEventEmitter<'foo' | 'baz'>(); typedEventEmitterNoArgs .on('foo', () => console.log('foo')) .on('baz', () => console.log('baz')); typedEventEmitterNoArgs.emit('baz');typedEventEmitterNoArgs.emit('foo');Using a type safe EventEmitter with one argument in listeners.
import TypedEventEmitter from 'typed-event-emitter-2'; class TypedEventEmitterOneArg extends TypedEventEmitter<never, { foo: number bar: string}> {} const typedEventEmitterOneArg = new TypedEventEmitterOneArg();typedEventEmitterOneArg .on('foo', (arg: number) => console.log(Math.abs(arg))) .on('bar', (arg: string) => console.log(arg.length)); typedEventEmitterOneArg.emit('foo', 1);typedEventEmitterOneArg.emit('bar', 'bar');Using a type safe EventEmitter with zero or one arguments in listeners.
import TypedEventEmitter from 'typed-event-emitter-2'; enum keys { baz, zoo,}; const typedEventEmitterMix = new TypedEventEmitter< keyof typeof keys, { foo: number bar: string }>(); typedEventEmitterMix .on('foo', (arg: number) => console.log(Math.abs(arg))) .on('bar', (arg: string) => console.log(arg.length)) .on('baz', () => console.log('baz')); typedEventEmitterMix.emit('foo', 1);typedEventEmitterMix.emit('bar', 'bar');typedEventEmitterMix.emit('zoo');License
typed-event-emitter-2 is licensed under the ISC License.