Node.js

Introduction

Created by Luis Ibanez

Node.js

Introduction

Javascript

Server-Side

Launch

Node.js

from a command line prompt

Simply type :

nodejs

Then hit the ENTER key.

Your prompt will now look like:

>

Let's try an addition:

> 2+2

Then hit the ENTER key.

and you will get

> 2+2
4

Variables

Let's create a variable:

> var fruit='apple'

Then hit the ENTER key.

Let's see it's value:

> fruit

Then hit the ENTER key.

and you will get

> fruit
'apple'

Let's change its value:

> var fruit='orange'

Then hit the ENTER key.

Let's see the new value:

> fruit

Then hit the ENTER key.

and you will get

> fruit
'orange'

"Variables"

are containers

that hold data.

the data in

"Variables"

can change.

by simply assigning

a new value to them

The value can be

a simple item...

Like a number

or a word

It can also be

a sentence...

Let's use a sentence as value:

> var book='The last of the Mohicans'

Then hit the ENTER key.

Let's see the value:

> book

Then hit the ENTER key.

and you will get

> book
'The last of the Mohicans'

Variables can also

hold a list of items...

Let's make a list:

> var groceries=['milk','eggs','bread']

Then hit the ENTER key.

Let's see the value:

> groceries

Then hit the ENTER key.

and you will get

> groceries
[ 'milk', 'eggs', 'bread' ]

We use the

square brackets [ ]

to define a list

We use the

comma symbol ","

to separate multiple items

> var groceries=['milk','eggs','bread']

Variables can also

hold a list of properties...

Let's set some properties:

> var kermit={'species':'frog','color':'green'}

Then hit the ENTER key.

Let's see the value:

> kermit

Then hit the ENTER key.

and you will get

> kermit
{ species: 'frog', color: 'green' }

We use the

curly brackets { }

to define a set of properties

We use the

colon symbol ":"

to separate the property key from its value

var foo = { key : value }

(This is a generic example. Do not type it)

We use the

comma symbol ","

to separate multiple properties

var foo = { key1 : value1, key2 : value2 }

(This is a generic example. Do not type it)

More properties

can be added dynamically

Let's add more about kermit

> kermit.girlfriend = 'peggy'

Let's see the changes:

> kermit

Then hit the ENTER key.

and you will get

> kermit
{ species: 'frog',
  color: 'green',
  girlfriend: 'peggy' }

Let's add more about kermit

> kermit.work = 'sesame street'

Let's see the changes:

> kermit

Then hit the ENTER key.

You know a lot about me!

Variables can also

hold a hierarchy...

Think:Tree !

Think:Tree !

Time to

Travel

Let's go on a trip:

> var world={}

Then hit the ENTER key.

Let's add continents as properties:

> world.africa = {}

Then hit the ENTER key.

Let's see the changes:

> world

Then hit the ENTER key.

and you will get

> world
{ africa: {} }

Let's add more continents as properties:

> world.europe = {}
> world.asia = {}
> world.austrasia = {}
> world.antartica = {}
> world.northamerica = {}

Let's see the changes

> world
{ europe: {},
  asia: {},
  austrasia: {},
  antartica: {},
  northamerica: {} }

Let's add countries as properties:

> world.europe.france = {}
> world.europe.england = {}
> world.europe.germany = {}
> world.europe.italy = {}
> world.europe.poland = {}

Let's see the changes

> world
{ europe: { france: {}, england: {}, germany: {}, italy: {}, poland: {} },
  asia: {},
  austrasia: {},
  antartica: {},
  northamerica: {} }

We can also inspect a specific branch

> world.europe
{ france: {}, england: {}, germany: {}, italy: {}, poland: {} }

Your

Turn !

Pick a

Continent

Add three

countries

to it

Pick a

Country

Add three

cities

to it

Pick a

City

Add a list of three food items

that you would like to eat there

Inspect the variable

at the level of the city

It should look like

> world.southamerica.brazil
{ saopaulo: {},
  riodejaneiro: { food: [ 'rodizio', 'mango', 'shrimp' ] },
  salvador: {} }

Let's exit

nodejs

type

process.exit();

Now you should be back

at the '$' prompt

in the command line

Breath!

Smile!