waveform-renderer/src/events/EventEmitter.ts

High-performance audio waveform visualization library for the web. Create customizable, interactive waveform renderers with TypeScript support and zero dependencies.

// eslint-disable-next-line @typescript-eslint/no-explicit-any
export class EventEmitter<Events extends Record<string, any>> {
    private events = new Map<keyof Events, Array<(args: Events[keyof Events & string]) => void>>();

    public off<E extends keyof Events>(event: E, callback: (args: Events[E]) => void): void {
        const callbacks = this.events.get(event);
        if (callbacks) {
            const index = callbacks.indexOf(callback as (args: Events[keyof Events]) => void);
            if (index !== -1) {
                callbacks.splice(index, 1);
            }
            if (callbacks.length === 0) {
                this.events.delete(event);
            }
        }
    }

    public on<E extends keyof Events>(event: E, callback: (args: Events[E]) => void): void {
        if (!this.events.has(event)) {
            this.events.set(event, []);
        }
        const callbacks = this.events.get(event)!;
        callbacks.push(callback as (args: Events[keyof Events]) => void);
    }

    public once<E extends keyof Events>(event: E, callback: (args: Events[E]) => void): void {
        const onceCallback = ((args: Events[E]) => {
            this.off(event, onceCallback);
            callback(args);
        }) as (args: Events[keyof Events]) => void;

        this.on(event, onceCallback);
    }

    public removeAllListeners<E extends keyof Events>(event?: E): void {
        if (event) {
            this.events.delete(event);
        } else {
            this.events.clear();
        }
    }

    protected emit<E extends keyof Events>(event: E, args: Events[E]): void {
        const callbacks = this.events.get(event);
        if (callbacks) {
            (callbacks as Array<(args: Events[E]) => void>).forEach(callback => callback(args));
        }
    }

    protected hasListeners<E extends keyof Events>(event: E): boolean {
        const callbacks = this.events.get(event);
        return callbacks ? callbacks.length > 0 : false;
    }
}