Question

我是es6和eventEmitter的新人。我已经准备了节点事件基础样式的模块，现在我正在尝试转换为es6 calass样式。这是

// eventStyle.js

const events = require('events');
const util = require('util');

var Customer = function() {
  // console.log(typeof this);
  events.EventEmitter.call(this);
  //    this is only public function
  this.register = function(email, password) {
  var newCustomer = {email:email, password:password}
  this.emit("newRegistation", newCustomer)
  }

  var _validate = function(customer) {
  if(customer.password=='password')
  this.emit("validated", customer)
  else
  this.emit("registationFailed", customer)
  }

  var _insert = function(customer) {
  this.emit("added", customer)
  }

  var _sendEmail = function(customer) {
  this.emit("emailSent", customer)
  }

  var _registationSuccessful = function(customer) {
  this.emit("registationSuccessful", customer)
  }

  this.on("newRegistation", _validate)
  this.on("validated", _insert)
  this.on("added", _sendEmail)
  this.on("emailSent", _registationSuccessful)
}

util.inherits(Customer, events.EventEmitter )

module.exports =客户

// eventApp.js

const Customer = require('./eventStyle');
customer = new Customer();
// console.log(customer);
customer.on("registationSuccessful", ()=>{
  console.log("well done");
})

customer.on("registationFailed", ()=>{
  console.log("sorry error");
})
console.log(typeof customer.register);
setTimeout(()=>customer.register(), 1000);

//现在我的基于es6的代码（不适用于我） eventStyle.js

const events = require('events');
const util = require('util');

class Customer {
  constuctor(){
  console.log("cons",this);
  events.EventEmitter.call(this);
  this.on("newRegistation", _validate)
  this.on("validated", _insert)
  this.on("added", _sendEmail)
  this.on("emailSent", _registationSuccessful)
  }

  //    this is only public function
  register(email, password) {
  var newCustomer = {email:email, password:password}
  console.log(this);
  this.emit("newRegistation", newCustomer)
  }

  _validate(customer) {
  if(customer.password=='password')
  this.emit("validated", customer)
  else
  this.emit("registationFailed", customer)
  }

  _insert(customer) {
  this.emit("added", customer)
  }

  _sendEmail(customer) {
  this.emit("emailSent", customer)
  }

  _registationSuccessful(customer) {
  this.emit("registationSuccessful", customer)
  }
}
util.inherits(Customer, events.EventEmitter )

module.exports =  Customer

有人告诉我错了什么。提前谢谢

Answer 1

五四个主要问题：

你错过了第一个＆＃39; r＆＃39;在constructor
在引用对象方法时需要使用this
~~您需要在回调中保留this（请参阅How to access the correct this inside a callback?）。~~在此特定的情况下，您不需要＆＃39;吨; EventEmitter on在this设置正确（reference）的情况下调用它们。如果没有提供该保证，您可以。
extends events行需要class（更常见的做法是调用导入EventEmitter然后使用extends EventEmitter）。< / p>
您不能使用此样式通过class events.EventEmitter.call(this);调用超级构造函数。相反，你打电话给super。您必须在使用this之前执行此操作。

所以最小变化版本是

class Customer extends events {

和constructor：

constructor() { // Added missing 'r' in "constructor"
    super();    // Added
    console.log("cons", this);
    // Removed `events.EventEmitter.call(this);` here
    // On all four of the following, note `this.`
    this.on("newRegistation", this._validate);
    this.on("validated", this._insert);
    this.on("added", this._sendEmail);
    this.on("emailSent", this._registationSuccessful);
}

但，如果您不希望_方法公开，则不需要将其公开;只需在构造函数中创建它们：

class Customer {
    constructor() {
        super();
        console.log("cons", this);

        const _validate = customer => {
            if (customer.password == 'password')
                this.emit("validated", customer);
            else
                this.emit("registationFailed", customer);
        };

        const _insert = customer => {
            this.emit("added", customer);
        };

        const _sendEmail = customer => {
            this.emit("emailSent", customer);
        };

        const _registationSuccessful = customer => {
            this.emit("registationSuccessful", customer);
        };

        this.on("newRegistation", _validate);
        this.on("validated", _insert);
        this.on("added", _sendEmail);
        this.on("emailSent", _registationSuccessful);
    }

    //    this is only public function
    register(email, password) {
        var newCustomer = {
            email: email,
            password: password
        }
        console.log(this);
        this.emit("newRegistation", newCustomer)
    }
}

第二种形式确实为每个实例创建了单独的函数对象，但其开销非常小。你需要数以百万计的班级实例才能解决问题。

您不必单独创建它们，您可以这样做：

this.on("newRegistration", customer => {
    if (customer.password == 'password')
        this.emit("validated", customer);
    else
        this.emit("registationFailed", customer);
});

......等等。但是如果你这样做了，那么这个函数就是匿名的，这在堆栈跟踪中没那么有用，如果出了什么问题。（const _validate = ...形式为have names的那些。）

关于调用super：如果要传递构造函数参数，可以使用其他表示法来执行此操作：

constructor(...args) {
    super(...args);
    // ...
}

Answer 2

差不多完成了，只缺少扩展到事件发射器并在构造函数中调用super来初始化超类（如果不这样做，this不存在）：

const events = require('events');
const util = require('util');

class Customer extends events {
  constructor(){
  super();
  console.log("cons",this);
  this.on("newRegistation", this._validate)
  this.on("validated", this._insert)
  this.on("added", this._sendEmail)
  this.on("emailSent", this._registationSuccessful)
  }

  //    this is only public function
  register(email, password) {
  var newCustomer = {email:email, password:password}
  console.log(this);
  this.emit("newRegistation", newCustomer)
  }

  _validate(customer) {
  if(customer.password=='password')
  this.emit("validated", customer)
  else
  this.emit("registationFailed", customer)
  }

  _insert(customer) {
  this.emit("added", customer)
  }

  _sendEmail(customer) {
  this.emit("emailSent", customer)
  }

  _registationSuccessful(customer) {
  this.emit("registationSuccessful", customer)
  }
}

module.exports =  Customer

功能为es6类基础样式

2 个答案: