JavaScript Essentials For Dummies

Title Page....3

Copyright Page....4

Table of Contents....7

Introduction....13

About This Book....14

Foolish Assumptions....14

Icons Used in This Book....15

Where to Go From Here....15

Chapter 1 JavaScript: The Big Picture....17

Adding JavaScript Code to a Web Page....17

The tag....17

Where do you put the <script> tag?....18

Example #1: Displaying a message to the user....19

Example #2: Writing text to the page....20

What You Need to Get Started....22

Dealing with Two Exceptional Cases....22

Handling browsers with JavaScript turned off....22

Handling very old browsers....24

Commenting Your Code....25

Moving to External JavaScript Files....26

Chapter 2 Programming with Variables....29

Getting Your Head around Variables....29

Declaring a variable with let....30

Storing a value in a variable....31

Checking out another way to declare a variable: const....33

Using variables in statements....34

Naming Variables: Rules and Best Practices....36

Rules for naming variables....36

Ideas for good variable names....36

Understanding Literal Data Types....38

Working with numeric literals....38

Exponential notation....39

Hexadecimal integer values....39

Working with string literals....40

Using quotation marks within strings....40

Understanding escape sequences....41

Working with Boolean literals....42

Chapter 3 Building Expressions....43

Understanding How Expressions Are Structured....43

Creating Numeric Expressions....44

Building String Expressions....45

Building Comparison Expressions....46

Building Logical Expressions....46

Understanding Operator Precedence....47

The order of precedence....47

Controlling the order of precedence....49

Chapter 4 Controlling the Flow of JavaScript....51

Decision-Making with if Statements....52

Branching with if. . .else Statements....53

Understanding the Value of Code Looping....55

Working with while Loops....56

Working with for Loops....59

Working with do. . .while Loops....63

Chapter 5 Harnessing the Power of Functions....67

Getting to Know the Function Structure....67

Making a Function Call....68

When the browser parses the <script> tag....69

When the page load is complete....70

When an event fires....72

Passing One or More Values to a Function....73

Passing one value to a function....74

Passing two or more values to a function....75

Getting a Value from a Function....77

Working with Anonymous Functions....78

Assigning an anonymous function to a variable....79

Replacing a function call with an anonymous function....80

Working with Arrow Functions....82

Chapter 6 Coding the Document Object Model....85

Getting Familiar with Objects....85

Working with object properties....86

Working with object methods....88

Introducing the Document Object Model....89

Specifying Elements in Your Code....91

Specifying an element by id....91

Specifying elements by tag name....91

Specifying elements by class name....92

Specifying elements by selector....92

Working with collections of elements....93

Touring the DOM with Code....95

Getting the children of a parent element....96

Getting all the child nodes....96

Getting the first child node....97

Getting the last child node....98

Getting the parent of a child element....99

Getting the siblings of an element....99

Getting the previous sibling....100

Getting the next sibling....100

Adding, Modifying, and Removing Elements....101

Adding an element to the page....101

Step 1: Creating the element....101

Step 2: Adding the new element as a child....102

Step 3: Adding text and tags to the new element....103

Inserting text or HTML into an element....104

Removing an element....105

Using Code to Mess Around with CSS....106

Changing an element’s styles....106

Adding a class to an element....106

Removing a class....108

Toggling a class....109

Using Code to Tweak HTML Attributes....109

Reading an attribute value....110

Setting an attribute value....110

Removing an attribute....111

Listening for Page Events....112

Chapter 7 Working with Arrays....117

What Is an Array?....117

Declaring an Array....118

Populating an Array....118

Declaring and populating an array at the same time....119

Populating an array using a loop....120

Iterating Arrays....121

Iterating an array: forEach()....121

Iterating to create a new array: map()....122

Iterating an array down to a value: reduce()....123

Iterating to locate an element: find()....124

Manipulating Arrays....126

The length property....126

Some useful array methods....126

Chapter 8 Coding Strings and Dates....129

Manipulating Strings....129

Working with string templates....130

Determining the length of a string....133

Searching for substrings....133

Learning the methods that extract substrings....134

Dealing with Dates and Times....135

Learning the arguments used with the Date object....136

Getting to know the Date object....137

Specifying the current date and time....137

Specifying any date and time....137

Getting info about a date....138

Setting the date....138

Chapter 9 Debugging JavaScript....141

Laying Out Your Debugging Tools....141

Debugging 101: Using the Console....143

Getting the console onscreen....144

Printing program data in the Console....144

Running code in the Console....145

Putting Your Code into Break Mode....146

Invoking break mode....147

Setting a breakpoint....147

Adding a debugger statement....148

Getting out of break mode....149

Stepping Through Your Code....149

Stepping one statement at a time....150

Stepping into some code....150

Stepping over some code....151

Stepping out of some code....152

Chapter 10 Dealing with Form Data....153

Coding Text Fields....153

Referencing by field type....154

Getting a text field value....155

Setting a text field value....155

Programming Checkboxes....156

Referencing checkboxes....157

Getting the checkbox state....157

Setting the checkbox state....158

Coding Radio Buttons....159

Referencing radio buttons....160

Getting a radio button state....160

Setting the radio button state....162

Programming Selection Lists....162

Referencing selection list options....163

Getting the selected list option....164

Changing the selected option....165

Working with Form Events....166

Setting the focus....167

Monitoring the focus event....167

Monitoring the blur event....168

Listening for element changes....168

Handling Form Data....170

Chapter 11 Ten JavaScript Debugging Strategies....173

Get Thee to Your Dev Tools....173

The Console Is Your Best Debugging Friend....174

Give Your Code a Break(point)....174

Step Through Your Code....174

Monitor Variable and Object Property Values....175

Indent Your Code....175

Break Down Complex Tasks....175

Break Up Long Statements....175

Comment Out Problem Statements....176

Use Comments To Document Your Scripts....176

Index....177

EULA....195

JavaScript Essentials For Dummies is your quick reference to all the core concepts about JavaScript―the dynamic scripting language that is often the final step in creating powerful websites. This no-nonsense book gets right to the point, eliminating review material, wordy explanations, and fluff. Find out all you need to know about the foundations of JavaScript, swiftly and crystal clear. Perfect for a brush-up on the basics or as an everyday desk reference on the job, this is the reliable little book you can always turn to for answers.

• Get a quick and thorough intro to the basic concepts of coding with JavaScript
• Review what you've already learned or pick up essential new skills
• Add interactive features to websites with JavaScript programming
• Keep this concise reference book handy for jogging your memory as you work

This book is to the point, focusing on the key topics you need to know about this popular programming language. Great for supplementing classroom learning, reviewing for a certification, or staying knowledgeable on the job.