JavaScript : A Beginner's Guide

561 Pages·2020·19.513 MB·English

by  John Pollock

BeginNew-Tight / JavaScript: A Beginner’s Guide, Fifth Edition / Pollock / 768-0 / Front Matter
Blind Folio: i
JavaScript
A Beginner’s Guide
Fifth Edition
John Pollock
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BeginNew-Tight / JavaScript: A Beginner’s Guide, Fifth Edition / Pollock / 768-0 / Front Matter
Blind Foli iii
To my wife, Heather, and children, Eva, Elizabeth, Elaine, and Evan,
Bruce and Joy Anderson, and Dr. J. D. and Linda Andrews

In memory of John and Betty Hopkins, James D. and
Livian Anderson, John William and Edith Hopkins,
Burley T. and Aline Price, “Doc” Flores, and Clifton Idom
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Blind Foli iv
About the Author
John Pollock is employed as a software developer during
the day and works on Web sites and other projects during
the evening. You can find him on Twitter (@ScripttheWeb)
or LinkedIn (https://www.linkedin.com/in/john-pollock-
82a2b074). John holds a Bachelor of Arts in English from Sam
Houston State University and currently lives in New Waverly,
Texas with his wife, Heather, and children, Eva, Elizabeth,
Elaine, and Evan.
About the Technical Editor
Christie Sorenson is a senior software engineer at ZingChart.
She has worked on JavaScript-based systems since 1997 and
has been fascinated with the evolution of the language. She
has collaborated and been the technical editor on several
JavaScript and HTML books. She holds a Bachelor of Science
in Computer Science from University of California, San Diego,
and now lives in San Francisco with her husband, Luke, and
daughters, Ali and Keira.
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Contents
ACKNOWLEDGMENTS ........................................................... xvi
INTRODUCTION .................................................................. xvii
1 Introduction to JavaScript ................................................ 1
What You Need to Know ............................................................ 2
Basic HTML and CSS Knowledge ............................................ 3
Basic Text Editor and Web Browser Knowledge ............................... 3
Which Version? ............................................................... 5
Client-Side and Server-Side Programming .................................... 6
Beginning with JavaScript .......................................................... 9
Prototype-Based .............................................................. 9
Interpreted Language ......................................................... 9
Numerous Environments ...................................................... 9
Putting It All Together .............................................................. 9
Online Resources ................................................................... 10
Try This 1-1: Use JavaScript to Write Text .......................................... 10
Chapter 1 Self Test ................................................................. 11
2 Placing JavaScript in an HTML File ..................................... 15
Using the HTML Script Tags ....................................................... 16
Identifying the Scripting Language ............................................ 17
Calling External Scripts ....................................................... 17
v v
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vi JavaScript: A Beginner’s Guide
Specifying when the Script Should Load ...................................... 18
Using <noscript></noscript> Tags ............................................ 18
Creating Your First Script ........................................................... 20
Writing a “Hello World” Script ............................................... 20
Creating an HTML Document for the Script .................................. 21
Inserting the Script into the HTML Document ................................. 21
Try This 2-1: Insert a Script into an HTML Document ............................... 23
Using External JavaScript Files ..................................................... 24
Creating a JavaScript File ..................................................... 24
Creating the HTML Files ..................................................... 24
Viewing the Pages in Your Browser ........................................... 26
Try This 2-2: Call an External Script from an HTML Document ..................... 27
Using JavaScript Comments ........................................................ 28
Inserting Comments on One Line ............................................. 28
Adding Multiple-Line Comments ............................................. 29
Chapter 2 Self Test ................................................................. 30
3 Using Variables ............................................................ 33
Understanding Variables ............................................................ 34
Why Variables Are Useful .......................................................... 35
Variables as Placeholders for Unknown Values ................................ 35
Variables as Time-Savers ..................................................... 35
Variables as Code Clarifiers ................................................... 36
Defining Variables for Your Scripts .................................................. 36
Declaring Variables ........................................................... 36
Assigning Values to Variables ................................................. 37
Naming Variables ............................................................. 39
Understanding Data Types .......................................................... 41
Number ...................................................................... 41
String ......................................................................... 42
Boolean ...................................................................... 47
Null .......................................................................... 47
Undefined .................................................................... 47
Symbol ....................................................................... 48
Object ........................................................................ 48
Try This 3-1: Declare Variables ..................................................... 49
Using Variables in Scripts ........................................................... 50
Making a Call to a Variable ................................................... 50
Adding Variables to Text Strings .............................................. 50
Writing a Page of JavaScript ........................................................ 54
Creating the Framework ...................................................... 54
Defining the Variables ........................................................ 54
Adding the Commands ....................................................... 55
Modifying the Page ........................................................... 56
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Contents vii
Try This 3-2: Create an HTML Page with JavaScript ................................ 58
Chapter 3 Self Test ................................................................. 60
4 Using Functions ........................................................... 63
What a Function Is .................................................................. 64
Why Functions Are Useful .......................................................... 64
Structuring Functions ............................................................... 65
Declaring Functions .......................................................... 65
Defining the Code for Functions .............................................. 66
Naming Functions ............................................................ 67
Adding Arguments to Functions ............................................... 67
Adding Return Statements to Functions ....................................... 69
Calling Functions in Your Scripts ................................................... 71
Script Tags: Head Section or Body Section .................................... 72
Calling a Function from Another Function .................................... 75
Calling Functions with Arguments ............................................ 76
Calling Functions with Return Statements ..................................... 81
Other Ways to Define Functions .............................................. 82
Try This 4-1: Create an HTML Page with Functions ................................. 86
Scope/Context Basics ............................................................... 87
Global Context ............................................................... 87
Function Context ............................................................. 88
Block Context ................................................................ 89
Try This 4-2: Write Your Own Functions ............................................ 90
Chapter 4 Self Test ................................................................. 91
5 JavaScript Operators ..................................................... 95
Understanding the Operator Types .................................................. 96
Understanding Arithmetic Operators ................................................ 97
The Addition Operator (+) .................................................... 98
The Subtraction Operator (–) .................................................. 101
The Multiplication Operator (*) ............................................... 101
The Division Operator (/) ..................................................... 102
The Modulus Operator (%) ................................................... 102
The Increment Operator (++) ................................................. 103
The Decrement Operator (– –) ................................................ 104
The Unary Plus Operator (+) .................................................. 105
The Unary Negation Operator (–) ............................................. 105
The Exponentiation Operator ................................................. 106
Understanding Assignment Operators ............................................... 106
The Assignment Operator (=) ................................................. 107
The Add-and-Assign Operator (+=) ........................................... 107
The Subtract-and-Assign Operator (–=) ....................................... 108
The Multiply-and-Assign Operator (*=) ....................................... 109
The Divide-and-Assign Operator (/=) ......................................... 109
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The Modulus-and-Assign Operator (%=) ...................................... 109
The Exponent-and-Assign Operator (**=) ..................................... 109
Try This 5-1: Adjust a Variable Value ................................................ 110
Understanding Comparison Operators ............................................... 111
The Is-Equal-To Operator (==) ................................................ 111
The Is-Not-Equal-To Operator (!=) ............................................ 113
The Strict Is-Equal-To Operator (===) ........................................ 114
The Strict Is-Not-Equal-To Operator (!==) .................................... 114
The Is-Greater-Than Operator (>) ............................................. 114
The Is-Less-Than Operator (<) ................................................ 115
The Is-Greater-Than-or-Equal-To Operator (>=) ............................... 116
The Is-Less-Than-or-Equal-To Operator (<=) ................................. 116
Understanding Logical Operators ................................................... 117
The AND Operator (&&) ..................................................... 117
The OR Operator (||) .......................................................... 117
The NOT Operator (!) ........................................................ 118
The Bitwise Operators ........................................................ 118
Special Operators ................................................................... 119
Understanding Order of Operations ................................................. 120
Try This 5-2: True or False? ......................................................... 121
Chapter 5 Self Test ................................................................. 123
6 Conditional Statements and Loops ....................................... 125
Defining Conditional Statements .................................................... 126
What Is a Conditional Statement? ............................................. 126
Why Conditional Statements Are Useful ...................................... 127
Using Conditional Statements ....................................................... 127
Using if/else Statements ...................................................... 127
Using the switch Statement ................................................... 137
Using the Conditional Operator ............................................... 139
User Input from a Prompt ..................................................... 140
Try This 6-1: Work with User Input ................................................. 143
Defining Loops ..................................................................... 144
What Is a Loop? .............................................................. 144
Why Loops Are Useful ....................................................... 144
Using Loops ........................................................................ 145
for ............................................................................ 145
while ......................................................................... 154
do while ...................................................................... 154
for in, for each in, and for of .................................................. 156
Using break and continue ..................................................... 156
Try This 6-2: Work with for Loops and while Loops ................................. 158
Chapter 6 Self Test ................................................................. 160
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Contents ix
7 JavaScript Arrays ......................................................... 163
What Is an Array? .................................................................. 164
Why Arrays Are Useful ............................................................. 165
Defining and Accessing Arrays ...................................................... 165
Naming an Array ............................................................. 165
Defining an Array ............................................................. 165
Accessing an Array’s Elements ............................................... 167
Using the length Property and Loops .......................................... 168
Changing Array Values and Changing the Length ............................. 169
Try This 7-1: Use Loops with Arrays ................................................ 171
Array Properties and Methods ...................................................... 172
Properties ..................................................................... 172
Methods ...................................................................... 173
Nesting Arrays ...................................................................... 189
Defining Nested Arrays ....................................................... 189
Loops and Nested Arrays ..................................................... 190
Try This 7-2: Nested Arrays Practice ................................................ 192
Chapter 7 Self Test ................................................................. 193
8 Objects .................................................................... 195
Defining Objects .................................................................... 196
Creating Objects .................................................................... 196
Naming ....................................................................... 196
Single Objects ................................................................ 197
Try This 8-1: Create a Computer Object ............................................. 200
Object Structures ................................................................... 201
Constructor Functions ........................................................ 201
Using Prototypes ............................................................. 206
The class Keyword ........................................................... 209
Helpful Statements for Objects ...................................................... 210
The for-in Loop ............................................................... 210
The with Statement ........................................................... 211
Try This 8-2: Practice with the Combination Constructor/Prototype Pattern .......... 212
Understanding Predefined JavaScript Objects ....................................... 213
The Navigator Object ......................................................... 214
The History Object ........................................................... 216
Chapter 8 Self Test ................................................................. 218
9 The Document Object ..................................................... 221
Defining the Document Object ...................................................... 222
Using the Document Object Model .................................................. 223
Using the Properties of the Document Object ........................................ 223
Collections ................................................................... 225
The cookie Property .......................................................... 226
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