@ingridsandev/chatbot-widget/src/utils/event-emitter.js

A framework-agnostic chatbot widget using Web Components

import logger from './logger.js';

class EventEmitter {
  constructor() {
    this.events = {};
    this.maxListeners = 10;
  }

  on(event, listener) {
    if (typeof listener !== 'function') {
      throw new TypeError('Listener must be a function');
    }

    if (!this.events[event]) {
      this.events[event] = [];
    }

    if (this.events[event].length >= this.maxListeners) {
      logger.warn(`MaxListenersExceededWarning: Possible EventEmitter memory leak detected. ${this.events[event].length + 1} ${event} listeners added.`);
    }

    this.events[event].push(listener);
    return this;
  }

  off(event, listener) {
    if (!this.events[event]) return this;
    
    if (!listener) {
      delete this.events[event];
      return this;
    }

    this.events[event] = this.events[event].filter(l => l !== listener);
    
    if (this.events[event].length === 0) {
      delete this.events[event];
    }

    return this;
  }

  emit(event, data) {
    if (!this.events[event]) return false;
    
    const listeners = [...this.events[event]];
    
    for (const listener of listeners) {
      try {
        listener(data);
      } catch (error) {
        logger.error(`Error in event listener for "${event}":`, error);
      }
    }

    return true;
  }

  once(event, listener) {
    const onceListener = (data) => {
      try {
        listener(data);
      } finally {
        this.off(event, onceListener);
      }
    };
    this.on(event, onceListener);
    return this;
  }

  removeAllListeners(event) {
    if (event) {
      delete this.events[event];
    } else {
      this.events = {};
    }
    return this;
  }

  listenerCount(event) {
    return this.events[event] ? this.events[event].length : 0;
  }

  setMaxListeners(n) {
    this.maxListeners = n;
    return this;
  }
}

export default EventEmitter;