nodejs中的EventEmitter

EventEmitter是nodejs核心的一部分。很多nodejs对象继承自EventEmitter，用来处理事件，及回调。来看API中的例子

var util = require("util");
var events = require("events");//EventEmitter通过events模块来访问

function MyStream() {//新建一个类
    events.EventEmitter.call(this);
}

util.inherits(MyStream, events.EventEmitter);//使这个类继承EventEmitter

MyStream.prototype.write = function(data) {//定义一个新方法
    this.emit("data", data);//在此触发名为"data"事件
}

var stream = new MyStream();

stream.on("data", function(data) {//注册监听器，监听名为"data"事件
    console.log('Received data: "' + data + '"');
})
stream.write("It works!"); // Received data: "It works!"

var util = require("util");
var events = require("events");//EventEmitter通过events模块来访问

function MyStream() {//新建一个类
    events.EventEmitter.call(this);
}

util.inherits(MyStream, events.EventEmitter);//使这个类继承EventEmitter

MyStream.prototype.write = function(data) {//定义一个新方法
    this.emit("data", data);//在此触发名为"data"事件
}

var stream = new MyStream();

stream.on("data", function(data) {//注册监听器，监听名为"data"事件
    console.log('Received data: "' + data + '"');
})
stream.write("It works!"); // Received data: "It works!"

可看出通过继承EventEmitter可为对象注册和触发相关事件。 可与Ruby做个比较，通过block来实现。

class MyStream
  def write(data)
    yield data
  end
end

stream = MyStream.new
stream.write('It works!') do |data|
  puts "Received data: #{data}"
end