4 Intro to ExpressJS

At the end of this section you’ll have a basic understanding of NPM, ExpressJS and templates.

Outline

• What is Express.JS
• What is NPM
• Your first Express Application
• Templates with DustJS

What is Express

Fast, unopinionated, minimalist web framework for Node.js

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

Simply, a tool to help you build things for the web.

What is NPM

NPM makes it easy for JavaScript developers to share and reuse code, and it makes it easy to update the code that you’re sharing.

DO NOT USE sudo npm install -g

NPM is a package manger for node. It controls local and global dependencies. If you already have Node.JS installed, you should have NPM. NPM keeps it’s information about your project in a package.json file.

{
  "name": "0-introduction-to-express",
  "version": "1.0.0",
  "description": "Introduction to ExpressJS",
  "main": "app.js",
  "dependencies": {
    "adaro": "^1.0.0-15",
    "express": "^4.12.4"
  }
}

To ensure that everything is operating normally run, npm -v .

NPM Tricks

• You can run npm init to help you scaffold your package.json file.
• For dependencies you can keep dev dependencies separate with --save-dev.
  • When deploying use, npm install --production.
• You can use git repositories as dependencies.
  • If you have version 1.1.65 or greater you can use GitHub URLs, "mocha": "mochajs/mocha"
  • More Information

Your first Express Application

Lets build a basic express app, with routes, some middleware and a template engine. All this work will take place in the folder train-headless/workspace/node/introduction-to-express.

This directory should empty, except for a .gitkeep file.

Setup

• Type npm init to get started creating out package.json file.
  • Most of these options don’t matter for this exercise. However the entry point should be app.js to be consistent with the finished examples.

Your prompt should look very similar to the following (I’ve removed some parts),

This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.

Press ^C at any time to quit.
name: (introduction-to-express)
version: (1.0.0)
description:
entry point: (index.js) app.js
test command:
git repository:
keywords:
author:
license: (ISC)
About to write to $HOME/Developer/training/train-headless/workspace/node/0-introduction-to-express/package.json:


Is this ok? (yes)

Create your *.js file. If you happened to have left the entry point value of your package.json as index.js, that’s fine.

• Run touch app.js, or touch index.js, depending on what the entry point is for your application.
• Run npm install --save express adaro. This will install local copies of the Express and Adaro libraries.

DO NOT USE sudo npm install -g

When working with Node.JS, in general, your dependencies are local to the project, not managed globally.

Creating your Application

At minimum, your application will create a new instance of the Express object and begin listening on a particular port.

Node uses the CommonJS module system. Node has a simple module loading system. In Node, files and modules are in one-to-one correspondence.

If the module identifier passed to require() is not a native module, and does not begin with /, ../, or ./, then Node starts at the parent directory of the current module, and adds /node_modules, and attempts to load the module from that location. If it is not found there, then it moves to the parent directory, and so on, until either the module is found, or the root of the tree is reached.

Node has several modules compiled into the binary.

At this point running, node app.js, this will yield nothing. However, if you have completed the setup tasks correctly, this will run without issues.

:boom:

(function () {
  var express = require('express'),
      app = express();

  app.listen(process.env.PORT || 3000);

  console.log('App is listening on %s', process.env.PORT);

  return app;
})();

Let’s add a few simple routes to the application. Express can respond to various HTTP verbs as API methods.

If you want to have a route listen on all methods, you can use .all()

app.get('/example', function (req, res) {
    res.send('Welcome to DrupalCon Barcelona.');
});

Express adds a simple .send() method to the response object. This abstracts away most of the boilerplate code to handle responses. We’ll look at some more interesting things to send in just a moment.

Start your app with node app.js, and visit http://USERNAME.dcbarcelona.4kclass.com:PORT/example in your browser.

Tell me what this matches on, and what it doesn’t.

Lets create a model object; you can use the sample below, and create a new route to send this object.

var model = {
  name: 'my-name',
  location: 'my-location',
  vice: 'Coffee'
};

Any ideas what will happen when you vist /api?

app.get('/api', function (req, res) {
  res.send(model);
});

Stop your app with ctrl+C and restart with node app.js to load this new route.

Maybe you want to send files.

Activities - Send File

• Require the path module
• Create a route that listens on the get HTTP method and serves the package.json file.
  • This is probably a bad idea in production, so just use this for an example.

var path = require('path');

app.get('/packagejson', function (req, res) {;
  res.sendFile(path.join(__dirname, 'package.json'));
});

---

• An absolute path is required to use res.sendFile()
• The join method from the path library accepts unlimited arguments and returns a string.
• __dirname is a global for the name of the directory that the currently executing script resides in.

Templates

Adaro - An expressjs plugin for handling DustJS view rendering. DustJS - A JavaScript templating engine. It inherits its look from the ctemplate family of languages, and is designed to run asynchronously on both the server and the browser.

• Require adaro.

var adaro = require('adaro');
app.set('views', 'views');
app.engine('dust', adaro.dust({cache: false}));
app.set('view engine', 'dust');

What is happening here?

---

• Let Express know where our views are located.
• Create an engine called dust that can be used later.
• Set the view engine to be the previously created engine, dust.
• Enable the use of the .render() method on the response.

Activities - Template Basics

• Create a template file, index.dust in ./views/.
• Use the following,

<html>
  <head>
    <title>WELCOME TO DrpalCon Barcelona</title>
  </head>
  <body>
    <h1>{name}, welcome to DrpalCon Barcelona.</h1>
    <h2>Check out my sweet blog.</h2>
  </body>
</html>

• Create a route that listens on the get HTTP method, and renders the model object against the template we just created.

---

app.get('/', function (req, res) {
  res.render('index', model);
});

• Listening on the home route.
• Using the index.dust template, with the model object as it’s data.

---

Activities - Intermediate Templates

• Create a posts.js with the following content, require this file.

module.exports = {
  name: 'Matthew',
  posts: [
    {
      'id': 1,
      'title': 'Welcome to DrpalCon Barcelona',
      'body': 'This is the first entry in my DrpalCon Barcelona travel log.',
      'published': '9/20/2015'
    },
    {
      'id': 2,
      'title': 'DrpalCon Barcelona is over.',
      'body': 'On my way home from DrpalCon Barcelona.',
      'published': '9/27/2015'
    }
  ]
}

• Create an article template, you can start from index.dust for this content.
  • Dust.JS documentation on looping, http://www.dustjs.com/guides/getting-started/#looping
• Create a route that listens on the get HTTP method, uses this article listing template, and renders the new content.

---

app.get('/articles', function (req, res) {
 res.render('articles', content);
});

<html>
  <head>
    <title>Articles from DrpalCon Barcelona</title>
  </head>
  <body>
    <h1>{name}, welcome to DrpalCon Barcelona.</h1>
    <h2>Check out my sweet blog.</h2>
    {#posts}
      <h3><a href="/article/{id}">{title}</a></h3>
      <p>{body}</p>
    {/posts}

  </body>
</html>

Activities - Advanced Templates

• Create an individual article template
• Create a route which modifies it’s output based on a query or route parameter.
  • Return just a single post matching on post.id