Carlos P. Jimeno

jimenocontact@gmail.com

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Carlos P. Jimeno

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Module 1.

Intro to backend technologies: Nodejs

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What is node.js

Node.js (sometimes called just Node for short) is a JavaScript runtime developed by Ryan Dahl. Dahl created Node because of the synchronous limitations of current web frameworks.

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Node is not

It is not a framework (there are frameworks built on top of Node.js though).
It is not a programming language (the language is still JavaScript).

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Intro & JS basics
Objects & Arrays
Functions
Callbacks, Promises & async
Node packages manager
Testing & linting
Express
Restify

Topics

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const, let & var

Variables

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Variables

// variable declaration

let name
let name, surmane, email

// variable asignament

let name
name = 'Karl'

// or inline
let name = 'Karl'

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Variables

// variable declaration

const name // throws an error

// variable declaration with asignament

const name = 'Karl'

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primitives & objects

Data types

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primitives

Data types

number
string
boolean
null
undefined

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Data types

Objects
Arrays
Functions

Non primitives

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Objects

Key-value relationship
Add, remove and modify keys and values in an object
Can access values in an Object with dot and bracket notations
List the properties of an Object

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Objects

// create an object
const user = {
  name: 'admin',
  pasword: '12345'
}

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Objects

const user = {
  name: 'Charlie',
  pasword: '12345'
}
//add attrs
user.isAdmin = true

// modify an attr
user.name = 'Homer'

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Objects

const user = {
  name: 'Charlie',
  pasword: '12345'
}

user.isAdmin = true

// delete an attr
delete user.isAdmin

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Objects

const user = {
  name: 'Charlie',
  pasword: '12345'
}

user.isAdmin = true

delete user.isAdmin

// attrs can be acces via [ ]
console.log(user['name'])

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Objects

const user = {
  name: 'Charlie',
  pasword: '12345'
}

user.isAdmin = true

delete user.isAdmin

console.log(user['name'])

Object.keys(user)

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Arrays

Basic & object lists
Understand advanced array methods
filter
reduce
map
clone an array

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Arrays

const myArray = [
  'Charlie',
  'Bob',
  'Petter'
]

const myArrayOfUsers = [
  {name: 'Charlie', age: 28},
  {name: 'Bob', age: 30},
  {name: 'Petter', age: 25}
]

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Arrays

// MAP
const array = [1, 2, 3]

// map each element to the value*2

const newArray = array.map(number => number * 2)

console.log(newArray) // <== [ 2, 4, 6 ]

.map()

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Arrays

// basic sintax
array.reduce((accumulator, currentValue) => accumulator + currentValue, initialValue)

const numbers = [12, 9, 1, 8]

const total = numbers.reduce((accumulator, currentValue) => {
  console.log("accumulator is: ", accumulator, "and current value is: ", currentValue)
  return accumulator + currentValue;
}, 0)

.reduce()

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Arrays

.filter()

// FILTER
var people = [
  { name: "Candice", age: 25 },
  { name: "Tammy", age: 30 },
  { name: "Allen", age: 20 },
  { name: "Nettie", age: 21 },
  { name: "Stuart", age: 17 },
  { name: "Bill", age: 19 }
]

//get the list of pepole older than 21 

const ofDrinkingAge = people.filter(person => person.age >= 21)

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Arrays

arrays practice

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Functions

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Functions

Declaration, invocations and returning values

// Function Declaration
function sayHelloWorld() {
  const whatToSay = 'Hello, World!';
  console.log(whatToSay);
}

// Function Invocation
sayHelloWorld(); // => Hello, World!


function sayHello(name) {
  console.log(`Hello ${name}!`);
}

// returning values
function printName(name){
  return name;
}

// return 
printName("Ana");

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Functions

anonymous

// anonymous function
setTimeout(function(){
    console.log("This is just an example of anonymous")
}, 1000);


// naming it...
function someFunctionName(){
    console.log("This is just an example of not anonymous")
}

setTimeout(someFunctionName, 1000);

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Functions

Arrow functions

let greeting = function(name) {
  console.log(`Hello, ${name}`);
}

// arrow function:
let greeting = name => {
  return name;
}

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Functions

Global vs local scope

// local scope
function sayHello() {
  let firstName = "Ana"; // <== local variable
  console.log(`Hello ${firstName}!`); 
}

sayHello(); // <== Hello Ana!
console.log(firstName); // <== ReferenceError: firstName is not defined


// global scope
const firstName = "Ana"; // <== global variable
function sayHello() {
  console.log(`Hello ${firstName}!`); 
}

sayHello(); // <== Hello Ana!
console.log(firstName); // <== Ana

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Functions

Global vs local scope

let firstName = "Ana"; // <== global variable
function sayHello() {
  let firstName = "Martina"; // <== local variable with the same name as the global one
  console.log(`Hello ${firstName}!`);
}

console.log(`Before the function executes the first name is ${firstName}.`); // <=
sayHello(); // <= 
console.log(`After the function executes the first name is ${firstName}.`); // <=

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Functions

Global vs local scope

let firstName = "Ana"; // <== global variable
function sayHello() {
  let firstName = "Martina"; // <== local variable with the same name as the global one
  console.log(`Hello ${firstName}!`);
}

console.log(`Before the function executes the first name is ${firstName}.`); // <= Ana
sayHello(); // <= Martina
console.log(`After the function executes the first name is ${firstName}.`); // <= Ana

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Greatest movies exercise

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Asyncronous

in JS

"JavaScript is not asynchronous language, but synchronous one with some asynchronous behaviors"

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Why async

single-threaded

only one block of code is executed at the time

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Why async

synchronous - the code gets executed line by line, from top to bottom, in the order in which they are put in

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Why async

🤔

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Why async

// hypothetical example

function readFile (file) {
  // read the file
  // veeeeeeeeeeeeeery large file
  return contentFile.length;
}

const textSize = readFile("odyssey.txt");
console.log(textSize); // => undefined

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Callbacks

Promises

Async & await

How async

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Callbacks


function someCallbackFunction(){
    console.log("Hey there, crew!!");
}

const timeoutId = setTimeout(someCallbackFunction, 1000);

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Promises

const myPromise = new Promise(function(resolve, reject) {  
   if (/* condition */) {
      resolve(/* value */);  // fulfilled successfully
   }
   else {
      reject(/* reason */);  // error, rejected
   }
});



myPromise.then((val) => console.log(val));

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Promises

const p1 = Promise.resolve(3);
const p2 = 1337;
const p3 = new Promise((resolve, reject) => {
  setTimeout(resolve, 100, 'foo');
}); 

Promise.all([p1, p2, p3]).then(values => { 
  console.log(values); // [3, 1337, "foo"] 
});

.all()

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Async await

async function f() {

  let promise = new Promise((resolve, reject) => {
    setTimeout(() => resolve("done!"), 1000)
  });

  let result = await promise; // wait till the promise resolves (*)

  console.log(result); // "done!"
}

f();

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Async practice

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Data types

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primitives

Data types

number
string
boolean
null
undefined

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Data types

Objects
Arrays
Functions

Non primitives

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Objects & functions

Data types

// Obects
let myCar = {
    make: 'Honda', 
    model: 'Accord', 
    year: 1998
}

// arrays

let cars = [
  'honda',
  'ford',
  'fiat'
]

// functions

funtion getCar(){
  return 'Honda'
}

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Data types

Objects & functions

value vs reference
clone (spread)
compare (JSON.stringify)

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Data types

let book1 = 'Harry Potter'
let book2 = book1
book1 = 'The power of now'
console.log(book1); // <==  The power of now
console.log(book2); // <==  Harry Potter

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Data types

const book1 = {
  author: "Charlotte Bronte"
}

const book2 = book1; // <== copy the book1 into the new object - book2

console.log(book1); // <== { author: 'Charlotte Bronte' }
console.log(book2); // <== { author: 'Charlotte Bronte' }

// CHANGE THE VALUE OF AUTHOR PROPERTY IN BOOK1:
book1.author = "Jane Austen";

// BOTH ARE CHANGED
console.log(book1); // <== { author: 'Jane Austen' }
console.log(book2); // <== { author: 'Jane Austen' }

// CHANGE THE VALUE OF AUTHOR PROPERTY IN BOOK2:
book2.author = "Edith Wharton";

// BOTH ARE CHANGED
console.log(book1); // <== { author: 'Edith Wharton' }
console.log(book2); // <== { author: 'Edith Wharton' }

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Data types


// object:
const book1 = {
  author: "Charlotte Bronte"
}
const book2 = book1; // <== copy the book1 into the new object - book2
console.log(book1 === book2); // <== true

// array:
const students = ['Ana', 'John', 'Fabio'];
const attending = students;
console.log(students === attending); // <== true

Compare by reference

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Data types

Copy in objects & arrays

const book1 = {
  author: "Charlotte Bronte"
}

const book2 = Object.assign({}, book1);

console.log(book2); // <== { author: "Charlotte Bronte" }
console.log(book1 === book2); // <== false



const students = ['Ana', 'John', 'Fabio'];
const attending = [...students];
students.push("Sandra");

console.log(students); // <== [ 'Ana', 'John', 'Fabio', 'Sandra' ]
console.log(attending); // <== [ 'Ana', 'John', 'Fabio' ]

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Node packages manager

npm

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npm is a package manager for Node

share your JavaScript code easily, using a command line tool.

Get track of the package versions

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npm --version

$ mkdir myNpm
$ cd myNpm
$ npm init

Create our fist project

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Lets try it!

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Our first package

https://nodemon.io/

reload automatically

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Our first package

1. Add nodemon

2. Add start script

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linting

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linting engines

https://jshint.com

https://standardjs.com/

https://eslint.org

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$ sudo npm i --global eslint

$ eslint --init

Add code extension

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Practice: create our fist linted project

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testing

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Our first testing enviroment

$ npm i jasmine --save-dev

$ sudo npm i --global jasmine

$ node node_modules/jasmine/bin/jasmine init

Initialize global

Initialize local

$ jasmine init

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Playing around with examples

$ jasmine examples

Config file

/spec/support/jasmine.json

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Config file

{
  // Spec directory path relative to the current working dir when jasmine is executed.
  "spec_dir": "spec",

  // Array of filepaths (and globs) relative to spec_dir to include and exclude
  "spec_files": [
    "**/*[sS]pec.js",
    "!**/*nospec.js"
  ],

  // Array of filepaths (and globs) relative to spec_dir to include before jasmine specs
  "helpers": [
    "helpers/**/*.js"
  ],

  // Stop execution of a spec after the first expectation failure in it
  "stopSpecOnExpectationFailure": false,

  // Run specs in semi-random order
  "random": false
}

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JS koans

The Koans are a series of assertions you must solve to understand how a programming language works

You get an assertion that is not passing a test.
You need to change/add code to make the test pass.

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http

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The request-response cycle

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Always check the console

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DNS

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HTTP

HTTP Hypertext Transfer Protocol.

Network protocol used to deliver all files and data on the World Wide Web

A protocol is simply a set of rules for communication, here between client and server

Clients use the rules of HTTP to send its requests to servers and servers respond using those rules as well

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HTTP verbs

GET / POST / DELETE ...

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Backend in JS

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Express hello world

$ mkdir express-hello-world

$ cd express-hello-world

$ npm init

$ npm install express --save

$ touch app.js

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Express hello world

edit our app.js

const express = require('express');

// We create our own server named app
// Express server handling requests and responses
const app = express();

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Express hello world

setup a route

const express = require('express')
const app = express()

// our first Route
app.get('/', (request, response, next) => {
  console.log(request)
  response.send('<h1>Welcome fellas</h1>')
})

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Express hello world

start the server

const express = require('express');
const app = express();

// our first Route
app.get('/', (request, response, next) => {
  console.log(request);
  response.send('<h1>Welcome fellas</h1>');
});

// Server Started
app.listen(3000, () => {
  console.log('My first app listening on port 3000!')
});

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Express hello world

$ node app.js

👉 visit localhost:3000

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Express hello world

Add nodemon

create our "start" script in out package.json

"start: : "nodemon app.js"

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Serving statics

Create a images folders and serve it

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Serving statics

$ mkdir public

$ mkdir public/images

$ curl -o public/images/cool-cat.jpg  https://wallpapercave.com/wp/X7VjxFk.jpg

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Serving statics

// ...
const app = express();

// Make everything inside of public/ available
app.use(express.static('public'));

// our first Route:
app.get('/', (request, response, next) => {
// ...

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Practice

Create a project with at least 3 pages

serve 4 pictures

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Express

Get methods

Route Params & Query string

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Express

Route params

app.get('/users/:username', (req, res, next) => {
  res.send(req.params);
})

Navigate to http://localhost:3000/users/devAcademy

{"username" :  "devAcademy"}

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Express

Query string

app.get('/search', (req, res, next) => {
  res.send(req.query)
})

http://localhost:3000/search?city=Barcelona

{"city" :  "Barcelona"}

http://localhost:3000/search?city=Barcelona&month=may

....

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Express

Post method

app.post('/login', (req, res) => {
  res.send('You\'ve logged in!');
});

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Express

Access to body data needs a parser

// ...
const bodyParser = require('body-parser');
// ...
app.use(bodyParser.urlencoded({ extended: true }));

$ npm i --save body-parser

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Express

The body parser

// ...
const bodyParser = require('body-parser');
// ...
app.use(bodyParser.urlencoded({ extended: true }));

$ npm i --save body-parser

Then we can access the request body

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Express

The body parser

app.post('/login', (req, res) => {
  res.send(req.body);
});

app.post('/login', (req, res) => {
  let email    = req.body.email;
  let password = req.body.password;
  
  res.send(`Email: ${email}, Password: ${password}`);
});

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Postman

APIs development tool

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Practice

app.post('/login', (req, res) => {
  // get aun user & password
  
  const users = [
    {
      username: 'admin',
      password: 'admin'
    },
    {
      username: 'admin2',
      password: 'admin2'
    }
  ]
  
  if (/* fill in this condition to be in users*/){
    // send an okay message
  } else {
    // send an invalid user or pass message
  }

})

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Express middlewares

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Express middlewares

// ...
app.use(myFakeMiddleware)
// ...
function myFakeMiddleware(){
  console.log("myFakeMiddleware was called!")
}

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Express middlewares

function myFakeMiddleware(_, _, next){
  console.log("myFakeMiddleware was called!");
  next();
}

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Express middlewares

function myFakeMiddleware(_, _, next){
  console.log("myFakeMiddleware was called!");
  next();
}

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Express middlewares

function myFakeMiddleware(req, _, next){
  console.log("myFakeMiddleware was called!")
  req.secretValue = "swordfish"
  next()
}


app.get('/test', (req, res) => {
  let mySecret = req.secretValue
  res.send(mySecret)
})

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Middleware Practice

Taking the login exercise

log something if the username is admin

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Express API practice

moviesAPI

Bonus: create an endpoint that takes email, subject and message and send an email to it

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Nodemailer

  let transporter = nodemailer.createTransport({
    service: 'Gmail',
    auth: {
      user: 'your email address',
      pass: 'your email password'
    }
  });
  transporter.sendMail({
    from: '"My Awesome Project 👻" <myawesome@project.com>',
    to: email, 
    subject: subject, 
    text: message,
    //you can add any custom template
    //html: `<b>${message}</b>`
  })

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Nodemailer

If not working with gmail try:

https://www.google.com/settings/security/lesssecureapps

Set the Access for less secure apps setting to Enable

tip:

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The restify project

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const restify = require('restify')

const server = restify.createServer()
const port = 3000

server.get('/hello/:name', (req, res, next) => {
  res.send('hello ' + req.params.name)
  next()
})

server.listen(port, function () {
  console.log(`App listening at: ${port}`)
})

Hello world

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server.use([
  function(req, res, next) {
    if (someCondition) {
      res.send('done!');
      return next(false);
    }
    return next();
  },
  function(req, res, next) {
    // if someCondition is true, this handler is never executed
  }
])

middleware examples

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Restify practice

moviesAPI

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