@anmiles/theme-switcher/src/lib/eventEmitter.ts

Theme switcher for websites

export class EventEmitter<TEventMap extends Record<string, Array<unknown>>> {
	private readonly listeners: {
		[TEvent in keyof TEventMap]?: Array<(...data: TEventMap[TEvent])=> void>
	} = {};

	public on<TEvent extends keyof TEventMap>(
		event: TEvent,
		listener: (...data: TEventMap[TEvent])=> void,
	): void {
		const listeners = this.listeners[event] ??= [];
		listeners.push(listener);
	}

	public off<TEvent extends keyof TEventMap>(
		event: TEvent,
		listener: (...data: TEventMap[TEvent])=> void,
	): void {
		const listeners = this.listeners[event] ??= [];
		listeners.splice(listeners.indexOf(listener), 1);
	}

	protected emit<TEvent extends keyof TEventMap>(
		event: TEvent,
		...data: TEventMap[TEvent]
	): void {
		this.listeners[event]?.forEach((listener) => {
			listener(...data);
		});
	}
}