chapter 3 functions, methods & objects what is a function?
TRANSCRIPT
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CHAPTER 3
FUNCTIONS, METHODS & OBJECTS
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WHAT IS A FUNCTION?
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Functions let you group a series of statements together to perform a specific task.
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Functions are reusable and save you from writing out the same code over and over.
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DECLARING A FUNCTION
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function
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function sayHello()
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function sayHello() { document.write(‘Hello’);}
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function sayHello() { document.write(‘Hello’);}
KEYWORD
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function sayHello() { document.write(‘Hello’);}
FUNCTION NAME
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function sayHello() { document.write(‘Hello’);}
CODE BLOCK (IN CURLY BRACES)
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CALLING A FUNCTION
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sayHello();
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sayHello();
FUNCTION NAME
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DECLARING A FUNCTION THAT
NEEDS INFORMATION
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function
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function getArea()
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function getArea(width, height)
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function getArea(width, height) { return width * height;}
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function getArea(width, height) { return width * height;}
PARAMETER PARAMETER
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function getArea(width, height) { return width * height;}
THE PARAMETERS ARE USED LIKE VARIABLES WITHIN THE FUNCTION
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CALLING A FUNCTION THAT NEEDS
INFORMATION
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getArea(3, 5);
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getArea(3, 5);
ARGUMENTS
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OBJECTS
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Objects group together variables and functions to create a model.
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In an object, variables and functions take on new names. They become properties and methods.
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Each property or method consists of a name (also known as a key) and its corresponding value.
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var hotel = {
name: ‘Quay’,
rooms: 40,
booked: 25,
gym: true,
roomTypes: [‘twin’, ‘double’, ‘suite’],
checkAvailability: function() {
return this.rooms - this.booked;
}
};
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var hotel = {
name: ‘Quay’,
rooms: 40,
booked: 25,
gym: true,
roomTypes: [‘twin’, ‘double’, ‘suite’],
checkAvailability: function() {
return this.rooms - this.booked;
}
};
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var hotel = {
name: ‘Quay’,
rooms: 40,
booked: 25,
gym: true,
roomTypes: [‘twin’, ‘double’, ‘suite’],
checkAvailability: function() {
return this.rooms - this.booked;
}
};
NAMES (KEYS)
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var hotel = {
name: ‘Quay’,
rooms: 40,
booked: 25,
gym: true,
roomTypes: [‘twin’, ‘double’, ‘suite’],
checkAvailability: function() {
return this.rooms - this.booked;
}
};
VALUES
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var hotel = {
name: ‘Quay’,
rooms: 40,
booked: 25,
gym: true,
roomTypes: [‘twin’, ‘double’, ‘suite’],
checkAvailability: function() {
return this.rooms - this.booked;
}
};
PROPERTIES
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var hotel = {
name: ‘Quay’,
rooms: 40,
booked: 25,
gym: true,
roomTypes: [‘twin’, ‘double’, ‘suite’],
checkAvailability: function() {
return this.rooms - this.booked;
}
};
METHOD
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ACCESSING OBJECTS
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var hotelName = hotel.name;
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var hotelName = hotel.name;
OBJECT
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var hotelName = hotel.name;
PROPERTY
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var hotelName = hotel[‘name’];
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var hotelName = hotel[‘name’];
OBJECT
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var hotelName = hotel[‘name’];
PROPERTY
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UPDATING OBJECTS
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hotel.name = ‘Park’;
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hotel.name = ‘Park’;
OBJECT
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hotel.name = ‘Park’;
PROPERTY
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hotel.name = ‘Park’;
NEW VALUE
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hotel[‘name’] = ‘Park’;
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hotel[‘name’] = ‘Park’;
OBJECT
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hotel[‘name’] = ‘Park’;
PROPERTY
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hotel[‘name’] = ‘Park’;
NEW VALUE
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BUILT-IN OBJECTS
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1
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Browser Object Model
THE WEB BROWSER
1
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BROWSER OBJECT MODELPROPERTIES INCLUDE:
window.innerHeight
window.innerWidth
window.screenX
window.screenY
METHODS INCLUDE:
window.print()
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21
Browser Object Model
THE WEB BROWSER
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1 2Document
Object Model
THE PAGE LOADED IN THE WEB BROWSER (OR TAB)
Browser Object Model
THE WEB BROWSER
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DOCUMENT OBJECT MODELPROPERTIES INCLUDE:
document.title
document.lastModified
METHODS INCLUDE:
document.write()
document.getElementById()
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31 2
Browser Object Model
THE WEB BROWSER
Document Object Model
THE PAGE LOADED IN THE WEB BROWSER (OR TAB)
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3Global
JavaScript Objects
GENERAL PURPOSE OBJECTS JAVASCRIPT NEEDS TO WORK
1 2Browser
Object Model
THE WEB BROWSER
Document Object Model
THE PAGE LOADED IN THE WEB BROWSER (OR TAB)
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GLOBAL JAVASCRIPT OBJECTSPROPERTIES INCLUDE:
saying.length
METHODS INCLUDE:
saying.toUpperCase()
saying.toLowerCase()
saying.charAt(3)
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