Created
April 15, 2023 05:10
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Type safe event emitter
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type Listener<Args extends Array<any>> = (...args: Args) => void; | |
class MyEmitter<EventMap extends Record<string, Array<any>>> { | |
private eventListeners: { | |
[K in keyof EventMap]?: Set<Listener<EventMap[K]>>; | |
} = {}; | |
constructor() {} | |
on<K extends keyof EventMap>( | |
eventName: K, | |
listener: Listener<EventMap[K]>, | |
) { | |
//super.on(eventName as string, listener as (...args: any) => void); | |
const listeners = this.eventListeners[eventName] ?? new Set(); | |
listeners.add(listener); | |
this.eventListeners[eventName] = listeners; | |
} | |
emit<K extends keyof EventMap>(eventName: K, ...args: EventMap[K]) { | |
const listeners = this.eventListeners[eventName] ?? new Set(); | |
for (const listener of listeners) { | |
listener(...args); | |
} | |
} | |
} | |
type User = { | |
name: string; | |
age: number; | |
}; | |
type sUser = { | |
dob: Date; | |
city: string; | |
} & User; | |
type EventMap = { | |
login: [user: User]; | |
signup: [user: sUser]; | |
logout: []; | |
}; | |
const emitter = new MyEmitter<EventMap>(); | |
emitter.on('login', (user) => { | |
console.log(user); | |
}); | |
emitter.on('signup', (user) => { | |
console.log('signup ', user); | |
}); | |
emitter.emit('login', { | |
age: 10, | |
name: 'John', | |
}); | |
emitter.emit('signup', { | |
age: 10, | |
city: 'New York', | |
dob: new Date(), | |
name: 'John', | |
}); |
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