JavaScript

Part 4 JavaScript - Part 4

Objects

Objects

Groups together variables and functions to create a model of something

Model is usually something you would recognize from the real world.
- Person
- Car
- Hotel
- ...

//HOTEL 1
var hotel1_name = "City Hotel";
var hotel1_numRooms = 100;
var hotel1_availableRooms = 30;

//HOTEL 2
var hotel2_name = "Waterfoot";
var hotel2_numRooms = 70;
var hotel2_availableRooms = 20;

Scenario: Hotel Booking Site

//HOTEL 1
var hotel1 = ["City Hotel",100,30];

//HOTEL 2
var hotel2 = ["Waterfoot",70,30];

Scenario: Hotel Booking Site

To get hotel1 available rooms you would need to do this:

//HOTEL 1
var availRooms1 = hotel1[2];

This is confusing and not meaningful.

What if this happened:

//HOTEL 3
var hotel3 = [40,60,"Bishops Gate"];

Objects

var hotel =
{
    name: "City Hotel",
    numRooms: 100,
    availRooms: 30;
};

hotel

{

name

City

Hotel

numRooms

100

availRooms

Objects

//retrieve using dot
var hotelName = hotel.name;

//retreive using bracket (similar to array)
var hotelName = hotel["name"];

hotel

{

name

City

Hotel

numRooms

100

availRooms

Retrieving Data from Object

Objects

//change value in an object
hotel.availRooms -= 1;

hotel.name = "CITY";

hotel

{

name

CITY

numRooms

100

availRooms

Updating Data in an Object

Properties and Methods

var hotel =
{
    name: "City Hotel",
    numRooms: 100,
    availRooms: 30
};

Properties

}

Properties are just a term used to describe variables in an object.

They are used to tell us about the object

Properties and Methods

var hotel =
{
    name: "City Hotel",
    numRooms: 100,
    availRooms: 30,

    numberBookedRooms: function()
    {
        return numRooms - availRooms;
    }
};

Properties

}

Method is a function within an object

Methods used to represent tasks associated with an object

Method

}

Constructors

function Hotel(name,rooms,available)
{
    this.name: name;
    this.numRooms: rooms;
    this.availRooms: available;

    this.numberBookedRooms: function()
    {
        return numRooms - availRooms;
    };
}

Create many objects that represent similar things

Constructors

function Hotel(name,rooms,available)
{
    this.name: name;
    this.numRooms: rooms;
    this.availRooms: available;

    this.numberBookedRooms: function()
    {
        return numRooms - availRooms;
    };
}

Constructor Defines the template

var cityHotel = new Hotel("City Hotel",100,30);

var waterfootHotel = new Hotel("Waterfoot",70,30);

Use the constructor to create object instances

Excercise

Create an object to represent a user.

Data relating to the following should be stored in the user object:

Name
Age
Address
Password
Email Address

The object should also have a method isOverage which return true id the user is over 18 and false otherwise.

Excercise

Create an object to represent an Account.

Data relating to the following should be stored in the user object:

Account No
Date Created
User Information (use the User object from previous excercise)
Account Active (yes or no)

The object should also have a method DeactivateAccount which should set Account Active to false and also set the users password to null so the user can no longer log in.