Node.js emitter.eventNames()用法及代碼示例

在Node.js中，大多數核心API都是圍繞慣用的異步和event-driven體係結構構建的。 EventEmitter類具有所有對象作為事件發出的實例，這些對象在這些實例中公開eventEmitter.on()函數。為了處理事件，有必要導入事件庫(require(‘events’))。

itter.eventNames()(在v6.0.0中添加)方法是事件模塊的內置應用程序編程接口，用於列出發射器已為其注冊偵聽器並以數組形式返回的事件。這些偵聽器的類型是字符串或符號。

用法:

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

參數：該函數不接受任何參數。

返回值<Array>：它返回一個包含字符串或Symbol值的數組，列出發射器已為其注冊偵聽器的事件。

範例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) ]

輸出：

Symbol(events.errorMonitor)

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

範例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());

使用以下命令運行index.js文件：

node index.js

輸出：

geeksforgeeks

print in console…

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

[ ‘alfa’, Symbol(newSymbolofGeekyWorld) ]

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

相關用法

注：本文由純淨天空篩選整理自vikas_g大神的英文原創作品 Node.js emitter.eventNames() Method。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。