初入nodejs,被一个题困惑了,求解答

此题来自nodeschool第二个教学模块Stream Adventure,这个题是第七题HTTP SERVER 题目的要求是把通过浏览器POST进来的内容转成大写直接输出给浏览器(最下面贴有完整题目)

我的实现如下

var tr = through(function(buf){
    this.queue(buf.toString().toUpperCase());
});

var server =  http.createServer(function(req,res){
  if(req.method == 'POST'){
    req.pipe(tr).pipe(res);
  }else{
    res.end('please send a post request');
  }

});
server.listen(Number(process.argv[2]));

但很可惜通不过测试,测试过程如下

ACTUAL EXPECTED

---

"YET" "YET"
"HOW" "HOW"
"TO" "TO"
"BURGEON." "BURGEON."
"IT'S" "IT'S"
"MEANT" !== "MILLIEMS"
"YET" !== "MEANT"
"HOW" !== "OF"
"TO" !== "MILLIEMS"
"BURGEON." !== "CENTIMENTS"
"IT'S" !== "OF"
"MILLIEMS" !== "DEADLOST"
"MEANT" !== "CENTIMENTS"
"OF" !== "OR"
"MILLIEMS" !== "DEADLOST"
"CENTIMENTS" !== "MISLAID"
"OF" !== "OR"
"DEADLOST" !== "ON"
"CENTIMENTS" !== "MISLAID"
"OR" !== "THEM"
"DEADLOST" !== "ON"
"MISLAID" !== "BUT,"

我发现开始数个测试都通过了,但是到了后面,发现输出的内容比输入慢,每次对应的输出都是之前输入的内容. 这是我比较疑惑的地方,为什么会出现这种情况.

而正确答案的代码是这样的

var http = require('http');
var through = require('through');

var server = http.createServer(function (req, res) {
    if (req.method === 'POST') {
        req.pipe(through(function (buf) {
            this.queue(buf.toString().toUpperCase());
        })).pipe(res);
    }
    else res.end('send me a POST\n');
});
server.listen(parseInt(process.argv[2]));

不知道这两种处理有什么区别,我只是把内建函数换成了变量.

题目的全部内容如下

HTTP SERVER

In this challenge, write an http server that uses a through stream to write back the request stream as upper-cased response data for POST requests.

Streams aren't just for text files and stdin/stdout. Did you know that http request and response objects from node core's http.createServer() handler are also streams?

For example, we can stream a file to the response object:

var http = require('http');
var fs = require('fs');
var server = http.createServer(function (req, res) {
    fs.createReadStream('file.txt').pipe(res);
});
server.listen(process.argv[2]);

This is great because our server can response immediately without buffering everything in memory first.

We can also stream a request to populate a file with data:

var http = require('http');
var fs = require('fs');
var server = http.createServer(function (req, res) {
    if (req.method === 'POST') {
        req.pipe(fs.createWriteStream('post.txt'));
    }
    res.end('beep boop\n');
});
server.listen(process.argv[2]);

You can test this post server with curl:

$ node server.js 8000 &
$ echo hack the planet | curl -d[@-](/user/-) http://localhost:8000
beep boop
$ cat post.txt
hack the planet

Your http server should listen on the port given at process.argv[2] and convert the POST request written to it to upper-case using the same approach as the TRANSFORM example.

As a refresher, here's an example with the default through callbacks explicitly defined:

var through = require('through')
process.stdin.pipe(through(write, end)).pipe(process.stdout);

function write (buf) { this.queue(buf) }
function end () { this.queue(null)

Do that, but send upper-case data in your http server in response to POST data.

Make sure to npm install through in the directory where your solution file lives.

To verify your program, run: stream-adventure verify program.js.