What is Node.js? (ICON UK)

2018
What is Node.js?
Tim Davis
The Turtle Partnership Ltd

About me
• Co-founder of The Turtle Partnership
• Working with Notes and Domino for over 20 years
• Working with JavaScript technologies and frameworks almost as
long
• Node, Angular, React, Material Design, Electron, Mongo, Couch,
Pouch, Google Cloud Platform
2

So, what is Node.js?
• It is a fully programmable server engine, programmed using Javascript
• Most of the time it is used as a web server
• It can
• serve web pages
• run APIs
• be a networked application
• do IoT stuff
• be containerised
3

Why are we interested?
• Will be integrated into Domino 10
• Allows access to Domino data from Node easily
• Parallel development path
• Extend existing Domino apps
• Mobile
• New websites
• Microservices
• Other platforms
4

Why use Node to do this?
• It is a hugely popular web platform
• Part of the MEAN/MERN development stacks
• Easy to add modules to do different things
• Lots of resources and support out there
• JavaScript, so works well with
• UI frameworks (Angular, React, etc)
• NoSQL datastores (MongoDB, CouchDB, etc)
• Domino 10 will be a JavaScript NoSQL datastore
5

Full Stack
• What is Full Stack development?
• It is using the same basic technology from the backend data up to the UI
• Here we are talking about using JavaScript.
• Typically this means a JavaScript UI framework, such as Angular or
React, with a JSON datastore on the backend
• JavaScript all the way down
• MEAN/MERN and now DEAN/NERD
6

Can I do JavaScript?
• If you have used JavaScript in Domino web forms
• maybe client-side validation scripts
• or some JQuery
• or in XPages server-side JavaScript
• …then you will be ﬁne with JavaScript in Node
• If you’ve used LotusScript, similar but different syntax
• e.g. variables, arrays, loops, functions
• …but has new stuff which is really great :-)
7

What about Domino 10?
• IBM/HCL will provide a domino connector module, 'domino-db'
• Add this to your Node app
• Can read and update your Domino databases
• Will use a new gRPC interface into Domino server
• fast, separate from the HTTP task
• Can use the upcoming Domino Query Language, DQL
• There will be an authentication solution, too: IAM, OAuth
8

But hey, enough of my yakkin’
• Where can I get it?
• How do I run it?
9

Download the installer
• Go to the Node.js website
• https://nodejs.org
• Download the installer
• Run the installer
• This installs two separate packages
• Node.js runtime
• npm package manager
• (npm is used to install add-on modules)
10

Run it!
• Open a terminal or command window, and type
node
• Opens a node shell
• (Press ctrl-c twice to close the shell)
• Doesn’t do very much
• At its core this is all Node is, an engine/interpreter
• To get it to do anything interesting we need some JavaScript
11

Our ﬁrst Node server
• Lets make a simple Node web server
• Start with a project folder to hold everything
• Create an empty JavaScript source ﬁle in it
• server.js
• Open this in your favourite code editor
• Mine is Visual Studio Code
• https://code.visualstudio.com
• Others suggest Webstorm
• Start writing some code…
12

Adding HTTP
• This is going to be a web server, so we need to handle HTTP
requests.
• Node has a built-in HTTP module, so let’s add this in
• We do this with the 'require' command 
const http = require('http'); 
• We can use 'require' to add any other modules we may need
13

Create a server object
• Now our Node app knows how to handle HTTP, let’s create a Node
HTTP server 
const server = http.createServer(…); 
• This will take a function as a parameter
• This function is the listener which tells it what to do when it receives
a request
14

Add a listener
const server = http.createServer((req, res) => {  
res.statusCode = 200;  
res.setHeader('Content-Type', 'text/plain');  
res.end('Hello World!n');  
}); 
• Don’t worry about the strange arrow =>, that is just a different way of saying function,
more on this later
• This acts on the request (req) and the response (res)
• Status 200 is 'success OK'
• Tells browser to expect some text
• Adds our text and tells the server to send the response
15

Tell it to start listening
const hostname = '127.0.0.1';
const port = 3000;
server.listen(port, hostname, () => {  
console.log(`Server running at  
http://$ {hostname}:${port}/`);  
}); 
• This tells the server to listen on port 3000 and prints a message to the
Node console
• This is all we need, only 11 lines of code.
16

Run our server
• Back in terminal or command window
• In our project folder, where server.js is, type
node server.js 
• The server starts running
• You will see the message displayed in the terminal/command window
• Browse to it on
http://127.0.0.1:3000 
• It says Hello World!
17

Let’s build a basic app
• We will modify our simple web server into the basis of a web app
• It will still respond with the Hello World message, but from this base
it can become anything
• Do this by adding in the Express module
• We will use npm to structure our app
• We will make our app standalone, so it can be portable and we can
control versions
• Even fewer lines of code!
18

What is Express?
• Add-on module
https://expressjs.com
• More sophisticated web functions
• Also hugely popular (it is the E in MEAN/MERN)
• Many other modules are built to integrate with it
• Including the Domino 10 connector module
19

Turning our server into an app
• We use the npm package manager
• It does almost all the work for us
• Start by initialising our app
npm init 
• This prompts for app name, etc, can just accept defaults for now
• Creates a package.json ﬁle
• Lists our server.js
• Start script is 'node server.js'
20

Install Node into our project
• We will install Node locally so everything is contained in one folder
• (We installed it globally from our download earlier)
• Install by typing
npm install node
• Creates new folder node_modules
21

Can run server using npm
• Uses the package.json conﬁguration
• We type
npm start 
• It runs the 'start' script in the package.json
• Notice this is the 'node server.js' command we used before
22

Adding Express
• Same as for all installs
npm install express 
• Automatically installs all the various modules that Express uses
• Adds 'express' to the dependencies in the package.json
23

Modify our server.js
• Replace Node's http module with express
const express = require('express') 
• Instead of the http server, we create an Express app
const app = express()
24

Add a route
• Routes are pattern matches for incoming URIs
• Sort of like Domino Web Site Rules
• Can have multiple routes to do different things
• Our route will listen for a regular browser 'get' request 
app.get('/', (req, res) => {
res.send('Hello World!')
} ) 
• The '/' means the root of our web server
25

Tell app to start listening
• Basically the same as the http version 
app.listen(port, hostname, () => {
console.log(`Server running at  
http://${hostname}:${port}/`);
}); 
• Only 10 lines of code!
• Run is same as before
npm start
26

So what is different?
• Isn't this just the same Hello World site?
• Now we have an app, with middleware routes
• For our processes and business logic
• The basic structure of any kind of web server, or networked app, or
microservice, or API
27

What else can we do?
• Get and update data
• Display a web page
• e.g. Angular or React front end
• Will be able to use the Domino 10 connector
npm install dominodb
28

Display a web page
• We can display static ﬁles from the ﬁle system
• These could be an Angular or React app
• Put these in a 'public' sub folder
• Default is index.html
• Add a route pointing to this sub folder
app.use(express.static(__dirname + '/public'));
• Requests hitting the root of the server '/' are redirected here
29

Catch-all route
• We can add a catch-all route after our static route, or any other routes we may use
• This will handle any other URLs people use and avoids 404 errors.
• We use a '/*' pattern to match anything 
app.get('/*', (req, res) => {
res.send('Another part of the site')
}) 
• The '/' is ﬁrst redirected by our static route, anything else will be caught by this
route
30

What about Domino?
• Install the Domino DB connector
npm install dominodb 
• Will be able to use code something like this in your routes: 
const { domServer } = require('domino-db');
domServer(serverConfig).then(
async (server) => {
const db = await server.useDatabase(dbConfig);
const docs = await db.bulkReadDocuments(query);
} 
• The query can be the new Domino Query Language
31

What else do we need to know?
• That is a basic Node app built
• Now I want to talk about some general JavaScript terms and
concepts
• JavaScript is improving all the time with new features that are used
in Node
• You will see them in examples and articles
• Knowing about these will make your life easier when starting out
32

JSON
• All the data in Node is JSON
• JavaScript Object Notation
• Hierarchical/nested like XML but much more readable
• Easily converted to and from strings
• Name/value pairs, "name":"value"
• Separated by commas
• Objects in curly brackets { }
• Arrays in square brackets [ ]
33

Sample JSON
let myJson = {
"name":"Tim",
"myArray":
[
{ "itemid":"0001" },
{ "itemid":"0002" },
{ "itemid":"0003" }
],
"quantity":5
}
34

Using JSON
• Can be passed around, used as parameters
• Can reference it by name and use dot notation to access or update
properties 
let myJson = {};
myJson.name = "Bob";
doSomethingWith( myJson.myArray[2].itemid );
const myString = JSON.stringify(myJson); 
35

NoSQL
• NoSQL is used to describe databases that do not use table-based
SQL data.
• Data is stored in documents and accessed in collections using
queries.
• Just like Domino!
• Usually uses JSON format.
• With v10, Domino becomes a proper NoSQL datastore able to ﬁt in a
full JS stack.
36

let and const
• These are almost always better than 'var'
• 'var' applies to whole enclosing function
• 'let' is like 'var' but the variable is limited to the current code block,
i.e. inside the curly brackets {}
• Can't let an existing let
• Helps avoid confusion
• 'const' is for values that will not change
• Get error if try to set another value
37

Arrow functions =>
• The arrow is similar to the traditional 'function', so
(arg1, arg2) => { ..code.. }
• kind of works like:
function ( arg1, arg2 ) { ..code.. }
• Difference is when you use 'this'
• with 'function', the 'this' is what calls the function
• with '=>', the 'this' is from outside what calls the function
• (More or less, it's worth reading up on)
• Great when passing functions as parameters in Node modules, where you want 'this' to
be the overall node app
38

Async
• JavaScript, and Node especially, are very very asynchronous.
• So what is asynchronous?
• 'Things do not happen in order'
• Async functions go off and do their thing and the rest of the code
continues.
• You may have already used async in Domino web forms when making
AJAX calls to web agents
• Great for loading rest of page while you look up something
• Annoying in code
39

Async example
function getDataAsync() {
… do a lookup …
console.log("got data");
}
console.log("start");
getDataAsync();
console.log("finish"); 
• The output is:
start
ﬁnish
got data
40

Callbacks
• The original way async functions allowed you to handle them:
myAsyncFunction( callback ) {…}
• Callback is a function that is called when the async function ﬁnishes.
• It usually receives the result of the async function as a parameter
• You can get a confusing chain of callbacks if you want to do more
async stuff with the results
41

Promises
• More readable
• Passes results to next function in a chain with '.then' 
doAsync1()
.then( (result1) => { return getAsync2(result1); })
.then( (result2) => { return getAsync3(result2); })
.then( (result3) => { etc } )
.catch( (error) => { handle error } ) 
• You can create your own Promise function by wrapping your async code with 'resolve'
and 'reject'
42

Promise.all
• How to handle multiple async processes in order?
• E.g. collection of documents, each of which needs handling in an async way
• Create an array of promises, then Promise.all to run them in order 
var promises = [];
for (var i = 0; i < collection.length; i++) {
promises.push( doAsyncStuff(collection[i]) );
}
Promise.all(promises).then(
function (results) {
//'results' is array of results in order
}
43

Async / Await
• Latest way of handling async functions 
async function doAsyncStuff() {
const value1 = await asyncFunction1();
const value2 = await asyncFunction2( value1 );
} 
• Avoids chains of callbacks or .thens
• Can use regular try/catch for error handling
• Can await your own promise functions
44

Summary
• What Node is
• How to build a simple Node app
• Why it is important for Domino 10
• Key JavaScript concepts
45

Questions
• Email: tim@turtlepartnership.com 
• Blog: https://turtleblog.info
46

What is Node.js? (ICON UK)

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