snek/src/snek/static/event-handler.js

export class EventHandler {
    constructor() {
        this.subscribers = {};
    }

    addEventListener(type, handler) {
        if (!this.subscribers[type]) this.subscribers[type] = [];
        this.subscribers[type].push(handler);
    }

    emit(type, ...data) {
        if (this.subscribers[type]) this.subscribers[type].forEach(handler => handler(...data));
    }
}