events.listenerCount(emitter, eventName)

• emitter <EventEmitter> 要查询的触发器
• eventName <string> | <symbol> 事件名称

一个类方法，返回在给定 emitter 上注册的指定 eventName 的监听器数量。

🌐 A class method that returns the number of listeners for the given eventName registered on the given emitter.

import { EventEmitter, listenerCount } from 'node:events';

const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2const { EventEmitter, listenerCount } = require('node:events');

const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2拷贝