JavaScript Objects
A car has properties like weight and color, and methods like
start and stop:
Object
Properties Methods
car.name = Fiat
car.model = 500
car.weight = 850kg
car.color = white
car.start()
car.drive()
car.brake()
car.stop()
All cars have the same properties, but the property values
differ from car to car.
All cars have the same methods, but the methods are performed
at different times.
JavaScript Objects
You have already learned that JavaScript variables are
containers for data values.
This code assigns a simple value (Fiat) to a variable named
car:
var car = "Fiat";
»
Objects are variables too. But objects can contain many
values.
This code assigns many values (Fiat, 500, white) to a
variable named car:
var car = {type:"Fiat",
model:"500", color:"white"};
»
The values are written as name:value pairs (name and value
separated by a colon).
JavaScript objects are containers for named values.
Object Properties
The name:values pairs (in JavaScript objects) are called
properties.
var person = {firstName:"John",
lastName:"Doe", age:50, eyeColor:"blue"};
Property Property Value
firstName John
lastName Doe
age 50
eyeColor blue
Object Methods
Methods are actions that can be performed on objects.
Methods are stored in properties as function definitions.
Property Property Value
firstName John
lastName Doe
age 50
eyeColor blue
fullName function()
{return this.firstName + " " + this.lastName;}
JavaScript objects are containers for named values called
properties or methods.
Object Definition
You define (and create) a JavaScript object with an object
literal:
Example
var person = {firstName:"John",
lastName:"Doe", age:50, eyeColor:"blue"};
»
Spaces and line breaks are not important. An object
definition can span multiple lines:
Example
var person = {
firstName:"John",
lastName:"Doe",
age:50,
eyeColor:"blue"
};
»
Accessing Object Properties
You can access object properties in two ways:
objectName.propertyName
or
objectName["propertyName"]
Example1
person.lastName;
»
Example2
person["lastName"];
»
Accessing Object Methods
You access an object method with the following syntax:
objectName.methodName()
Example
name = person.fullName();
»
If you access the fullName method, without (), it will return
the function definition:
Example
name = person.fullName;
»
A method is actually a function definition stored as a
property value.
Do Not Declare Strings, Numbers, and Booleans as Objects!
When a JavaScript variable is declared with the keyword
"new", the variable is created as an object:
var x = new String(); // Declares x as a String object
var y = new Number(); // Declares y as a Number object
var z = new Boolean(); // Declares z as a Boolean object
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