node . js emitter . event name()方法
原文:https://www . geesforgeks . org/node-js-emitter-event names-method/
在 Node.js 中，大多数核心 API 都是围绕一个惯用的异步和事件驱动架构构建的。EventEmitter 类拥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。为了处理事件，需要导入事件库( require(【事件】))。
emitter . event name()(在 v6.0.0 中添加)方法是事件模块的一个内置应用编程接口，用于列出 emitter 已注册侦听器的事件，并以数组形式返回。这些侦听器的类型可以是字符串或符号。
语法:
const EventEmitter = require('events');
emitter.eventNames()
参数:此功能不接受任何参数。
返回值 < 数组 > : 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:
符号(events.errorMonitor)
['阿卡什'，'哈迪'，符号(newSymbolofGeekyWorld)】
示例 2: 文件名:
// 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
在控制台中打印……
【‘connect something’，【alfa’，Symbol(newSymbolofGeekyWorld)】
【‘alfa’，Symbol(newSymbolofGeekyWorld)】
参考:https://nodejs . org/API/events . html # events _ emitter _ event name
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