[筆記] Express

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Express

install

• yarn add express
• starter - Express
• Route：用來決定哪個 URL 會跑到哪一個 Function 去

template engine

• yarn add ejs
• 開一個 views 的資料夾
• Using template engines with Express - Express
• EJS
• 範例：

  // app.js
  app.set('view engine', 'ejs')
  app.get('/', function (req, res) {
    res.render('index', {
        message: req.query.name || 'Hello there!'
    });
  });

  <!-- views/index.ejs -->
  <h1>hello <%= message %></h1>

static file

• 靜態頁面
• app.use(express.static('public'))
• 可直接存取 localhost:3000/public/index.html，不用寫 app.get(){}

額外補充資料

• Node.js Express 初入門 – 上集 - 寫點科普，請給指教。
• Node JS-Back end見聞錄 - 2018 iT 邦幫忙鐵人賽

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MVC

View

• 顯示

Model

• 負責與資料庫溝通
• 範例：(未串資料庫)

  // model/user.js
  module.exports = {
    getUser: (callback) => {
        callback({
            name: 'abc'
        })
    }
  }

  // app.js
  const userModel = require('./model/user')
  app.get('/', function (req, res) {
    userModel.getUser((user)=>{
        res.render('index',{
            message: user.name
        })
    })
  });

Controller

• 邏輯層，通常用來跟 Model 溝通，再將資料傳進 View，把結果傳回去

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DB

mysql

• yarn add mysql
• Database integration MySQL - Express

• 範例：

  // model.js
  const mysql = require('mysql');
  const connection = mysql.createConnection({
  host     : '',
  user     : '',
  password : process.env.PWD || '',  // 不直接將密碼寫在 code 中，在 cli 中 `PWD=password node model.js` 
  database : ''
  });
  
  connection.connect();
  
  connection.query('SELECT * FROM users', function (error, results, fields) {
  if (error) throw error;
  console.log('response', results);
  })
  
  connection.end()

  • 密碼也可以另外寫在 run.sh，PWD=password node model.js，run.sh 記得放在 .gitignore 裡；執行時，cli 指令為 sh run.sh

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Middleware

• 在收到 request 與回傳 response 中間做一些事情

Session

• yarn add express-session
• session - Express
• 範例：

  
  const session = require('express-session');
  app.use(session({ secret: 'keyboard cat', cookie: { maxAge: 60000 }}));

app.get('/', function (req, res) { const username = req.session.username; res.render('index',{ message: username ? username : 'not login' }) });

// 設置 session app.get('/login', function(req, res) { req.session.username = 'abc'; res.send('login success'); })

// 清 session app.get('/logout', function(req, res) { req.session.destroy(); res.send('clear session'); })

```javascript
// 給 model 的範例
app.get('/login', function(req, res) {
    userModel.login(req.query.username, req.query.password, function(result){
        if(result){
            req.session.username = result.username;
            res.redirect('/');
        }else{
            res.send('login fail');
        }
    })
})

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ORM

• Object Relational Mapping
• 用 object 的方式與資料庫欄位做對應，就可以不用下 SQL

Sequelize

• yarn add sequelize
• Sequelize
• 範例：

  
  // ./model/db.js
  const Sequelize = require('sequelize');

const db = new Sequelize('database', 'username', 'password', { host: '', dialect: 'mysql', }); db .authenticate() .then(() => { console.log('Connection has been established successfully.'); }) .catch(err => { console.error('Unable to connect to the database:', err); });

module.exports = db;

```javascript
// ./model/user.js
const Sequelize = require('sequelize');
const db = require('./db');

const User = db.define('user', {
    u_id: {
        type: Sequelize.INTEGER,
        primaryKey: true,
        autoIncrement: true
    },
    username: {
        type: Sequelize.STRING(20)
    },
    password: {
        type: Sequelize.STRING(256)
    },
    nickname: {
        type: Sequelize.STRING(64)
    },
    avatar: {
        type: Sequelize.STRING(500)
    },
    status: {
        type: Sequelize.BOOLEAN,
        defaultValue: true
    },
    create_time: {
        type: Sequelize.DATE,
        defaultValue: Sequelize.NOW
    },
    update_time: {
        type: Sequelize.DATE
    }
}, {
    tableName: 'zzly00_users',
    createdAt: false,
    updatedAt: false
});

User.sync();

module.exports = User;

// app.js
const User = require('./model/user');

app.get('/', (req, res) => {
    User
        .create({username: 'test', password: 'aaa', nickname: 'test'})
        .then(() => {
            console.log('created');
        })
})

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其他 Library

nodemon

• yarn add nodemon
• 可以偵測檔案修改，並重跑 node，不需要自己重開
• 在 package.json scripts 裡加上 "start": "nodemon ./app.js"，就可以在 cli 中下指令 npm run start
• nodemon

pm2

• yarn add pm2 -g
• 可以讓程式跑在背景中
• pm2