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.
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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.js read: I think, read: therefore read: I am. read: Rene Descartes readable readable readable Message Complete Process 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.js Name: Carolinus Color: Green Data: {"name":"Carolinus","color":"Green","handled":true} Name: Solarius Color: Blue Data: {"name":"Solarius","color":"Blue","handled":true} Name: Lo Tae Zhao Color: Gold Data: {"name":"Lo Tae Zhao","color":"Gold","handled":true} Name: Ommadon Color: Red Data: {"name":"Ommadon","color":"Red","handled":true} Process finished with exit code 0
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