Introduction xxxi
 
Chapter 1: The New Toys In ES2015-ES2020, and Beyond 1
 
Definitions, Who's Who, and Terminology 2
 
What are the "New Toys"? 4
 
How Do New Toys Get Created? 6
 
Keeping Up with the New Toys 9
 
Using Today's Toys in Yesterday's Environments, and Tomorrow's Toys Today 10
 
Review 15
 
Chapter 2: Block-Scoped Declarations: Let and Const 17
 
An Introduction to let and const 18
 
True Block Scope 18
 
Repeated Declarations are an Error 19
 
Hoisting and the Temporal Dead Zone 20
 
A New Kind of Global 22
 
const: Constants for JavaScript 24
 
Block Scope in Loops 26
 
Old Habits to New 36
 
Chapter 3: New Function Features 39
 
Arrow Functions and Lexical this, super, etc. 40
 
Default Parameter Values 45
 
"Rest" Parameters 50
 
Trailing Commas in Parameter Lists and Function Calls 52
 
The Function name Property 53
 
Function Declarations in Blocks 55
 
Function Declarations in Blocks: Standard Semantics 57
 
Old Habits to New 60
 
Chapter 4: Classes 65
 
What is a Class? 66
 
Introducing the New class Syntax 66
 
Comparing with the Older Syntax 75
 
Creating Subclasses 77
 
Leaving Off Object.prototype 97
 
new.target 98
 
class Declarations vs. class Expressions 101
 
More to Come 103
 
Old Habits to New 104
 
Chapter 5: New Object Features 105
 
Computed Property Names 106
 
Shorthand Properties 107
 
Getting and Setting an Object's Prototype 107
 
Method Syntax, and super Outside Classes 109
 
Symbol 112
 
New Object Functions 120
 
Symbol.toPrimitive 123
 
Property Order 125
 
Property Spread Syntax 127
 
Old Habits to New 128
 
Chapter 6: Iterables, Iterators, For-Of, Iterable Spread, Generators 131
 
Iterators, Iterables, the for-of Loop, and Iterable Spread Syntax 131
 
Generator Functions 146
 
Old Habits to New 163
 
Chapter 7: Destructuring 165
 
Overview 165
 
Basic Object Destructuring 166
 
Basic Array (and Iterable) Destructuring 169
 
Defaults 170
 
Rest Syntax in Destructuring Patterns 172
 
Using Different Names 173
 
Computed Property Names 174
 
Nested Destructuring 174
 
Parameter Destructuring 175
 
Destructuring in Loops 178
 
Old Habits to New 179
 
Chapter 8: Promises 181
 
Why Promises? 182
 
Promise Fundamentals 182
 
Using an Existing Promise 186
 
Adding Handlers to Already Settled Promises 201
 
Creating Promises 202
 
Other Promise Utility Methods 207
 
Promise Patterns 210
 
Handle Errors or Return the Promise 210
 
Promises in Series 211
 
Promises in Parallel 213
 
Promise Subclasses 218
 
Old Habits to New 219
 
Chapter 9: Asynchronous Functions, Iterators, and Generators 221
 
async Functions 222
 
async Iterators, Iterables, and Generators 232
 
for-await-of 238
 
Old Habits to New 238
 
Chapter 10: Templates, Tag Functions, and New String Features 241
 
Template Literals 241
 
Improved Unicode Support 250
 
Iteration 255
 
New String Methods 256
 
Updates to the match, split, search, and replace Methods 259
 
Old Habits to New 260
 
Chapter 11: New Array Features, Typed Arrays 263
 
New Array Methods 264
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