Node.js

Node.js

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HTTP Request & Response

HTTP

A piece of code is worth a thousand words.

var http = require('http');

http.createServer(function (req, res) {
    res.statusCode = 200;// 304
    res.end('fromHttpServer');
}).listen(5000);

http.createServer

HTTP Request

In last week...

var http = require('http');
var host = '127.0.0.1';

http.createServer(function (req, res) {

console.log(req.method + ' ' + req.url + ' HTTP/' + req.httpVersion);

console.log('Host:' + host);
}).listen(5000, host);

HTTP Response

Last week
You have to send valid HTML response.

res.statusCode = 200;
res.setHeader('Content-Type', 'text/html');

var body = 
'<html>'+
'<head>'+
'<title>An Example Page</title>'+
'</head>'+
'<body>'+
'Hello World, this is a very simple HTML document.'+
'</body>'+
'</html>'

res.setHeader('Content-Length', body.length);
res.end(body);

Callback is Asynchronous

var port = 5000;

console.log('before calling http.createServer');
http.createServer(function (req, res) {

console.log(req.method + ' ' + req.url + ' HTTP/' + req.httpVersion);

res.end('ok');
}).listen(port, host, function () {

console.log('HTTP server started at ' + host + ':' + port);
});
console.log('http.createServer and .listen called');

File System

File System

Another place to deal with asynchronous APIs
However, they do provide synchronous versions. (postfixed with *Sync)
fs.readFile
fs.readFileSync

Callbacks

The asynchronous form always take a completion callback as its last argument.
The arguments passed to the completion callback depend on the method,
but the first argument is always reserved for an exception.

Read File Example

var fs = require('fs');

fs.readFile('./package.json', function (err, data) {
if (err) { throw err; }
console.log('Your project name is ' + data.name + ' with keywords ' + data.keywords);
// console.log('---');
// console.log(data);
});

Send JSON File to Client

fs.readFile('./package.json', 'utf8', function (err, data) {
if (err) { throw err; }
res.setHeader('Content-Type', 'application/json');
res.end(data);
});

JSON formatter Chrome Extension

List Files Example

File Upload Form

What if I want to add more routes?

Or output dynamic contents not just only simple length!

It's a mess!

Express.js

Comes to rescue

routing problem
static files serving
dynamic view rendering

Initialize

npm install express@3.x.x --save 3.x.x is very IMPORTANT
var express = require('express');
Wait! require works here?

Module

The Module System has three type of modules :

Core Modules : http, fs, url
File Modules : index.js, package.json
Loading from node_modules folders : express, q

require Module are CACHED

Usage

API docs => express.js@3.x.x

The MVC Pattern

Model–view–controller (MVC) is a software pattern for implementing user interfaces.

Template Engine

ejs : Embedded JavaScript
npm install ejs
app.set('view engine', 'ejs');
put your .ejs under views directory
call res.render to generate HTML

Includes for common parts

It's annoying to write duplicated HTMLs
Let's extract them using include

<head>
<meta charset="utf-8">
<title><%= title %></title>
</head>

Extract Controller Codes

What's controller?
It handles request and provides response for client
Use module.exports to create controller module

Models

So we have views and controllers, what about models?

Use a Database such as MySQL or MongoDB
Use File System to read/save data
Commit
fs with relative files writes to process.cwd

Extract Model Codes

Model(data) is the core of applications
We may use it again and agian everywhere in applications
Extracting them to independent module is always a good idea
__dirname

剩下就是你們的事了