Learning JavaScript, 3rd Edition: Add Sparkle and Life to Your Web Pages

347 Pages·2015·3.55 MB·English

by  Ethan Brown

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THIRD EDITION
Learning Javascript
Ethan Brown
Boston
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Learning JavaScript
by Ethan Brown
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Table of Contents
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii
1. Your First Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Where To Start 20
The Tools 20
A Comment on Comments 22
Getting Started 23
The JavaScript Console 25
jQuery 26
Drawing Graphics Primitive 26
Automating Repetitive Tasks 28
Handling User Input 29
Hello World 31
2. JavaScript Development Tools. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Writing ES6 Today 33
ES6 Features 34
Installing Git 35
The Terminal 35
Your Project Root 36
Version Control: git 36
Package Management: npm 39
The Transcompilers 41
Build Tools: Gulp and Grunt 42
Project Structure 43
Running Babel with Gulp 44
Linting 45
Recap 48
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3. Literals, Variables, Constants, and Data Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Variables and Constants 51
Identifier Names 53
Literals 54
Primitive Types and Objects 54
Numbers 56
Strings 57
Escaping 58
Special Characters 59
Template Strings 60
Multiline Strings 60
Numbers as Strings 61
Booleans 62
Symbols 62
Null and Undefined 63
Objects 63
Number, String, and Boolean Objects 66
Arrays 66
Trailing Commas in Objects and Arrays 68
Dates 68
Regular Expressions 69
Maps and Sets 69
Data Type Conversion 70
Converting to Numbers 70
Converting to String 71
Converting to Boolean 71
Conclusion 71
4. Control Flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
A Control Flow Primer 73
While Loops 77
Block Statements 77
Whitespace 78
Helper Functions 79
if…else Statement 80
Do-While Loop 81
For Loop 82
If Statement 83
Putting it all Together 84
Control Flow Statements in JavaScript 85
Control Flow Exceptions 86
Chaining if-else Statements 86
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Metasyntax 87
Additional for Loop Patterns 88
switch Statements 89
for…in loop 92
for…of loop 93
Useful Control Flow Patterns 93
Using continue to Reduce Conditional Nesting 93
Using break or return to Avoid Unnecessary Computation 94
Using Value of Index after Loop Completion 95
Using Descending Indexes When Modifying Lists 95
Conclusion 96
5. Expressions and Operators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Operators 99
Arithmetic Operators 99
Operator Precedence 102
Comparison Operators 103
Comparing Numbers 105
String Concatenation 106
Logical Operators 106
Truthy and Falsy Values 107
AND, OR, and NOT 107
Short-Circuit Evaluation 109
Logical Operators with Non-Boolean Operands 109
Conditional Operator 110
Comma Operator 111
Grouping Operator 111
Bitwise Operators 111
typeof Operator 113
void Operator 114
Assignment Operators 114
Destructuring Assignment 115
Object & Array Operators 117
Expressions in Template Strings 118
Expressions and Control Flow Patterns 118
Converting if…else Statements to Conditional Expressions 118
Converting if Statements to Short-Circuited Logical OR Expressions 118
Conclusion 119
6. Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Return Values 122
Calling vs. Referencing 122
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Function Arguments 123
Do Arguments Make the Function? 125
Destructuring Arguments 126
Default Arguments 127
Functions as Properties of Objects 127
The this Keyword 128
Function Expressions and Anonymous Functions 130
Arrow Notation 131
call, apply and bind 132
Conclusion 134
7. Scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Scope vs. Existence 136
Lexical vs. Dynamic Scoping 136
Global Scope 137
Block Scope 139
Variable Masking 140
Functions, Closures, and Lexical Scope 141
Immediately-Invoked Function Expressions (IIFEs) 142
Function Scope and Hoisting 143
Function Hoisting 145
The Temporal Dead Zone 146
Strict Mode 146
Conclusion 147
8. Arrays and Array Processing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
A Review of Arrays 149
Array Content Manipulation 150
Adding or Removing Single Elements at the Beginning or End 151
Adding Multiple Elements at the End 151
Getting a Sub-Array 152
Adding or Removing Elements At any Position 152
Cutting and Replacing Within an Array 152
Filling an Array with a Specific Value 153
Reversing and Sorting Arrays 153
Array Searching 154
The Fundamental Array Operations: map and filter 156
Array Magic: reduce 158
Array Methods and Deleted or Never-Defined Elements 161
String Joining 161
Summary 162
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9. Objects and Object-Oriented Programming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Property Enumeration 165
for…in 166
Object.keys 166
Object-Oriented Programming 167
Class and Instance Creation 168
Dynamic Properties 169
Classes are Functions 170
The Prototype 171
Static Methods 173
Inheritance 174
Polymorphism 175
Enumerating Object Properties, Revisited 176
String Representation 177
Multiple Inheritance, Mixins, and Interfaces 177
Conclusion 179
10. Maps and Sets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Maps 181
Weak Maps 183
Sets 184
Weak Sets 185
Breaking the Object Habit 185
11. Exceptions and Error Handling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
The Error Object 187
Exception Handling with try and catch 188
Throwing Errors 189
Exception Handling and the Call Stack 189
try…catch…finally 191
Let Exceptions be Exceptional 192
12. Iterators and Generators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
The Iteration Protocol 195
Generators 197
yield Expressions and Two-Way Communication 198
Generators and return 201
Conclusion 201
13. Functions, and the Power of Abstract Thinking. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
Functions as Subroutines 203
Functions as Subroutines That Return a Value 204
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Functions as…Functions 205
So What? 207
Functions are Objects 208
IIFEs and Asynchronous Code 209
Function Variables 211
Functions in an Array 212
Pass a Function into a Function 214
Return a Function from a Function 215
Recursion 216
Conclusion 217
14. Asynchronous Programming. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
The Analogy 220
Callbacks 220
setInterval and clearInterval 221
Scope and Asynchronous Execution 222
Error-First Callbacks 223
Callback Hell 224
Promises 225
Creating Promises 226
Using Promises 226
Events 228
Promise Chaining 230
Preventing Unsettled Promises 231
Generators 232
One Step Forward and Two Steps Back? 235
Don’t Write Your Own Generator Runner 236
Exception Handling in Generator Runners 236
Conclusion 237
15. Date and Time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Dates, Time Zones, Timestamps, and the Unix Epoch 239
Constructing Date Objects 240
Moment.js 241
A Practical Approach to Dates in JavaScript 242
Constructing Dates 242
Constructing Dates on the Server 242
Constructing Dates in the Browser 243
Transmitting Dates 243
Displaying Dates 244
Date Components 245
Comparing Dates 246
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