Node.js 发射器.eventNames() 方法

在 Node.js 中，大多数核心 API 都是围绕惯用的异步和事件驱动架构构建的。 EventEmitter 类具有由所有对象作为事件发出的实例，其中这些对象公开了一个eventEmitter.on()函数。必须导入事件库（ require('events') ）才能处理事件。

发射器.eventNames() （在v6.0.0中添加）方法是事件模块的内置应用程序编程接口，用于列出发射器已注册监听器的事件并以数组形式返回。这些侦听器的类型是字符串或符号。

句法：

const EventEmitter = require('events');
emitter.eventNames()

参数：此函数不接受任何参数。

Return Value < Array > ：它返回一个包含字符串或符号值的数组，列出发射器已注册侦听器的事件。

示例 1：文件名：index.js

// Node.js program to demonstrate the 
// emitter.eventNames() method 
  
// Using require to access events module 
const EventEmitter = require('events');
  
// Creating new event Emitter
const newEventEmitter = new EventEmitter();
  
// Creating new event akash
newEventEmitter.on('akash', () => {});
  
// Creating new event hadii
newEventEmitter.on('hadii', function() {});
  
// Error monitor function
console.log(EventEmitter.errorMonitor);
  
// Creating new symbol event newSymbol
const newSym = Symbol('newSymbolofGeekyWorld');
newEventEmitter.on(newSym, () => {});
  
// Printing event Names
console.log(newEventEmitter.eventNames());
// Prints: [ 'akash', 'hadii', 
// Symbol(newSymbolofGeekyWorld) ]

输出：

Symbol(events.errorMonitor)

[ ‘akash’, ‘hadii’, Symbol(newSymbolofGeekyWorld) ]

编程需要懂一点英语

示例 2：文件名：index.js

// Node.js program to demonstrate the 
// emitter.eventNames() method 
  
// Using require to access events module 
const EventEmitter = require('events');
  
// Creating new event Emitter
const newEventEmitter = new EventEmitter();
  
// Creating a new callback function 
const someCallback = () => {
  console.log('Connected to something!');
};
  
// Creating new event connectSomething
newEventEmitter.on('connectSomething', someCallback);
  
// Creating new event alfa
newEventEmitter.prependListener('alfa', () => console.log('b'));
  
// Creating new event alfa, not added to eventnames array...
newEventEmitter.once('geeksforgeeks', 
() => console.log('print in console...'));
  
// Creating new event alfa, not added to eventnames array...
newEventEmitter.prependOnceListener('geeksforgeeks', 
() => console.log('geeksforgeeks'));
  
// Emitting geeksforgeeks event
newEventEmitter.emit('geeksforgeeks');
  
// Creating new symbol event newSymbolofGeekyWorld
const newSym = Symbol('newSymbolofGeekyWorld');
newEventEmitter.on(newSym, () => {});
  
// Printing event Names
console.log(newEventEmitter.eventNames());
  
// Removing connectSomething event
newEventEmitter.removeListener('connectSomething', someCallback);
  
// Printing event Names
console.log(newEventEmitter.eventNames());

使用以下命令运行index.js文件：

node index.js

输出：

geeksforgeeks

print in console…

[ ‘connectSomething’, ‘alfa’, Symbol(newSymbolofGeekyWorld) ]

[ ‘alfa’, Symbol(newSymbolofGeekyWorld) ]

编程需要懂一点英语

参考： https://nodejs.org/api/events.html#events_emitter_eventnames