Node.md

Basic Server Setup

const http = require('http');

// takes in request + response objects
const server = http.createServer((req, res) => {
    console.log('request made');
});

// port, hostname (localhost is default)
server.listen(3000, 'localhost', () => {
    console.log('listening for requests on port 3000');
})

Requests & Responses

Many of these functions can be managed through the Express package

req.url

• Returns the URL appended to the hostname (ex. localhost:3000/home)

req.method

• Returns type of request (ex. GET)

Writing Reponses

3 steps:

1. Set header content
2. Write browser response
3. End response

const http = require('http');
const fs = require('fs');

// takes in request + response objects
const server = http.createServer((req, res) => {
    // set header content type
    res.setHeader('Content-Type', 'text/html');

    // send html file
    fs.readFile('./views/index.html', (err, data) => {
        if(err) {
            console.err(err);
            res.end();
        } else {
            // write html data
            // res.write(data);
            res.end(data); // shorthand
        }
    })
});

// port, hostname (localhost is default)
server.listen(3000, 'localhost', () => {
    console.log('listening for requests on port 3000');
})

URL paths

let path = './views/';
switch(req.url){
    case '/':
        path += 'index.html';
        res.statusCode = 200;
        break;
    case '/about':
        path += 'about.html';
        res.statusCode = 200;
        break;
    default:
        path += '404.html';
        res.statusCode = 404;
        break;
}
// send html file
fs.readFile(path, (err, data) => {
    ...
}

Status Codes

• Describe response type sent to browser
  • 200 - OK
  • 301 - Redirect
  • 404 - Not found
  • 500 - Server error
• Set the responses in the switch statement (when we send the HTML pages)

Redirects

case '/about-me':
    res.statusCode = 301;
    res.setHeader('Location', '/about');
    res.end();
    break;

• Redirect /about-me to /about
  • In the switch statement, set the header to ('Location', '/about')

Express

const express = require('express');

// express app
const app = express();

// listen for requests on port 3000
app.listen(3000);

// the below app.get functions are similar to a large switch statement in raw node

// home page
app.get('/', (req, res) => {
    // automatically sends header + status code
    // res.send('<p>html response</p>');
    // specify that the ./ root directory is the current directory (__dirname)
    res.sendFile('./views/index.html', { root: __dirname });
})

// about page
app.get('/about', (req, res) => {
    res.sendFile('./views/about.html', { root: __dirname });
})

// redirects
app.get('/about-us', (req, res) => {
    res.redirect('/about');
})

// default case (always runs if there is no match above)

// 404 page
app.use((req, res) => {
    res.status(404).sendFile('./views/404.html', { root: __dirname });
})

View Engines

• Inject dynamic data into webpages

EJS

• Generate HTML with JavaScript
  • We can use EJS to display dynamic content
  • Replace .html with .ejs

// app.js updated with view engine
const express = require('express');
const app = express();

// listen for requests on port 3000
app.listen(3000);

// register view engine
app.set('view engine', 'ejs');

// express looks for views inside the ejs-views folder
app.set('views', 'ejs-views');

// home page
app.get('/', (req, res) => {
    // pass in dynamic data as object
    res.render('index', { title: 'title' });
})

// 404 page
app.use((req, res) => {
    res.status(404).render('404', { title: '404' });
})

Embed Javascript into .ejs files

// write javascript
<% const name = 'korosensei' %>
// output variable
<%= name %> // korosensei

Partials

• Reusable EJS components

// include the nav component 
<% - include('./partials/nav.ejs') %>

Middleware

• Functions that run on the server between the requests going in and the responses going out
• They run top to bottom (similar to a switch statement)

app.use(), app.get(), are all examples of middleware

next

app.use((req, res, next) => {
    console.log('new request');
    console.log('host: ', req.hostname);
    console.log('path: ', req.path);
    console.log('method: ', req.method);
    next();
})

• As we are not returning a response back to the browser, the app hangs unless we use the next() function (similar to a continue)
• Continue on with the rest of the code

Static Files

• Access images/css files

app.use(express.static('public'));

• Files in the public folder can now be accessed by the server

Mongoose

• MongoDB object modelling for Node

// connect to mongodb
const dbURI = 'paste db link here, remember to replace the username, password, and DB name fields'

// connect to db (async)
mongoose.connect(dbURI, { useNewUrlParser: true, useUnifiedTopology: true })
    .then(result => {app.listen(3000)}) // only listen to requests once connected to db
    .catch(err => console.log(err));

Schemas/Models

• Schemas define data/document structure
  • Define properties and property types
• Models are created based on schemas

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const blogSchema = new Schema({
    // describe blog structure
    title: {
        type: String,
        required: true,
    },
    body: {
        type: String,
        required: true
    },
}, { timestamps: true });

// Create a model implementing the blog schema
const Blog = mongoose.model('Blog', blogSchema);
module.exports = Blog;

• Since the model name is Blog, we look for the Blog collection in MongoDB