Typesafe Event Emitter

EventEmitter.ts

export class OpenEventEmitter<T> implements EventEmitter<T> {
    private readonly handlers: { [eventName in keyof T]?: ((value: T[eventName]) => void)[] }

    constructor() {
        this.handlers = {}
    }

    getClosedEmitter(): EventEmitter<T> {
        return this
    }

    emit<K extends keyof T>(event: K, value: T[K]): void {
        this.handlers[event]?.forEach(h => h(value))
    }

    on<K extends keyof T>(event: K, handler: (value: T[K]) => void): void {
        if(!this.handlers[event])
            this.handlers[event] = []
        this.handlers[event]?.push(handler)
    }
}

export default interface EventEmitter<T> {
    on<K extends keyof T>(event: K, handler: (value: T[K]) => void): void
}