# Node.js - Building a serever
Node comes with its own `http` built-in module

## using `http` module

const http = require('http'); // grab the 'http' module

const server = http.createServer( ()=> {
    //console.log('headers', request.headers)
    console.log('method', request.method)
    console.log('url', request.url)

    const user = {
        name: 'John',
        hobby: 'Skating'
    }

    response.statusCode = 200;
    response.setHeader('Content-Type', 'application/json');
    response.end(JSON.stringify(user));
})

server.listen(3000);

- `const http = require('http');`: grab the buit-in `http` module
- `http.createServer( (req, res) ⇒ {…} )`: The `createServer()` method of `http` creates a new HTTP server and returns it.
- `server.listen(3000)`: open a port `3000`

### Run the file

$ node server.js

1. Go to [localhost:3000](http://localhost:3000/) (nothing seems to happen)
2. Back to terminal: `server.js` is running in Node

## Add params: `request` & `response`

const http = require('http'); 

// create server
const server = http.createServer( (request, response)=> {
    console.log('headers', request.headers);
    console.log('methods', request.method);
    console.log('url', request.url);
    
    response.setHeader('Content-Type', 'text/HTML');
    response.end('<h1>Helllloooooo</h1>');
});

server.listen(3000);

### request
對方要求進入 web server，關於使用者的詳細資訊物件 (e.g. `request.url`)

### response
* response.statusCode
* response.setHeader('Content-Type', 'application/json')
* response.end()

## 相關 API 語法

const http = require("http");

// create server
http.createServer(function(req,res){
 res.writeHead(200,{"Content-Type":"text/plain"})
 res.write("Hello")
 res.end()
}).listen(8080);

Another way: take out the function

const requestListener = async(req, res)=>{
    console.log(req.url);
    res.end();
}

const server = http.createServer(requestListener);
server.listen(8080);

- header info
- `.writeHead( 200, {"Content-Type":"text/plain"} )`
- `200`: statusCode
- `{"Content-Type":"text/plain"}`
- `.setHeader('Content-Type', 'text/HTML')`
- `.write`
- `.end()` - 結束這次的請求
- `.listen(8080)` - 開啟一個 port

## port

`127.0.0.1:3000`

- `127.0.0.1` - 由自己的電腦所開啟的 web server 伺服器 (`localhost`)
- `:3000` - 伺服器其中一個軟體，佔據電腦裡其中一個 port `3000`
- `:21` - ftp
- `:3389` - 遠端桌面

## Run the file
Use nodeman we've set before:

$npm start

Visit [localhost:3000](http://localhost:3000/):
- `Status Code`: 200
- `Content-Type`: text/HTML

Back to terminal & check the request:

## Example: Grab a JSON file

const http = require('http'); // grab the http module

const server = http.createServer( (request, response)=> {   
    //create an object
    const user = {
      name: 'John',
      hobby: 'skating'
    } 
    
    // set content-type to JSON
    response.setHeader('Content-Type', 'application/JSON');
    
    // turn the object into JSON
    response.end(JSON.stringify(user)); 
})

server.listen(3000);