Node.js的Duplex流和Transform流怎么使用

这篇文章主要介绍“node.js的Duplex流和TransfORM流怎么使用”的相关知识，小编通过实际案例向大家展示操作过程，操作方法简单快捷，实用性强，希望这篇“node.js的Duplex流和Transform流怎么使用”文章能帮助大家解决问题。

Duplex流一个很好的例子是tcp套接字连接.需要实现_read(size)和_Write(data,encoding,callback)方法.

var stream = require('stream');var util = require('util');util.inherits(Duplexer, stream.Duplex);function Duplexer(opt) {  stream.Duplex.call(this, opt);  this.data = [];}Duplexer.prototype._read = function readItem(size) {  var chunk = this.data.shift();  if (chunk == "stop"){    this.push(null);  } else{    if(chunk){      this.push(chunk);    }  }};Duplexer.prototype._write = function(data, encoding, callback) {  this.data.push(data);  callback();};var d = new Duplexer({allowHalfOpen:true});d.on('data', function(chunk){  console.log('read: ', chunk.toString());});d.on('readable',function(){  console.log("readable");})d.on('end', function(){  console.log('Message Complete');});d.write("I think, ");d.write("therefore ");d.write("I am.");d.write("Rene Descartes");d.write("stop");

输出结果：

"C:\Program Files (x86)\JetBrains\WEBStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe stream_duplex.jsread:  I think, read:  therefore read:  I am.read:  Rene DescartesreadablereadablereadableMessage CompleteProcess finished with exit code 0

Transform变换流扩展了Duplex流，不需要实现而是直接提供。但要实现_transform(chunk,encoding,callback)._flush()这个方法不知道用来做什么的目前

var stream = require("stream");var util = require("util");util.inherits(JSONObjectStream, stream.Transform);function JSONObjectStream (opt) {  stream.Transform.call(this, opt);};JSONObjectStream.prototype._transform = function (data, encoding, callback) {  object = data ? JSON.parse(data.toString()) : "";  this.emit("object", object);  object.handled = true;  this.push(JSON.stringify(object));  callback();};var tc = new JSONObjectStream();tc.on("object", function(object){  console.log("Name: %s", object.name);  console.log("Color: %s", object.color);});tc.on("data", function(data){  console.log("Data: %s", data.toString());});tc.write('{"name":"Carolinus", "color": "Green"}');tc.write('{"name":"Solarius", "color": "Blue"}');tc.write('{"name":"Lo Tae Zhao", "color": "Gold"}');tc.write('{"name":"Ommadon", "color": "Red"}');

输出结果：

"C:\Program Files (x86)\JetBrains\WebStorm 11.0.3\bin\runnerw.exe" F:\nodejs\node.exe stream_transform.jsName: CarolinusColor: GreenData: {"name":"Carolinus","color":"Green","handled":true}Name: SolariusColor: BlueData: {"name":"Solarius","color":"Blue","handled":true}Name: Lo Tae ZhaoColor: GoldData: {"name":"Lo Tae Zhao","color":"Gold","handled":true}Name: OmmadonColor: RedData: {"name":"Ommadon","color":"Red","handled":true}Process finished with exit code 0

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