Computer und IT

JavaScript

ALL OF JAVASCRIPT'S NEWEST FEATURES, IN DEPTH, MADE EASY TO UNDERSTAND.JavaScript is a rapidly changing language and it can be challenging to keep up with all the new toys being added. JavaScript: The New Toys explores the newest features of the world's most popular programming language while also showing readers how to track what's coming next. After setting the stage by covering who manages the process of improving JavaScript, how new features get introduced, terminology, and a high-level overview of new features, it details each new or updated item in depth, with example uses, possible pitfalls, and expert recommendations for updating old habits in light of new features. JavaScript: The New Toys:* Covers all the additions to JavaScript in ES2015-ES2020 plus a preview of what's coming next* Explores the latest syntax: nullish coalescing, optional chaining,```let```and```const```,```class```syntax, private methods, private fields,```new.target```, numeric separators, BigInt, destructuring, default parameters, arrow functions,```async```functions,```await```, generator functions,```...```(rest and spread), template literals, binary and octal literals,```**```(exponentiation), computed property/method names,```for-of```,```for-await-of```, shorthand properties, and others* Details the new features and patterns including modules, promises, iteration, generators, Symbol, Proxy, reflection, typed arrays, Atomics, shared memory, WeakMap, WeakSet, and more* Highlights common pitfalls and explains how to avoid them* Shows how to follow the improvements process and even participate in the process yourself* Explains how to use new features even before they're widely supportedWith its comprehensive coverage and friendly, accessible style, JavaScript: The New Toys provides an invaluable resource for programmers everywhere, whether they work in web development, Node.js, Electron, Windows Universal Apps, or another JavaScript environment.About the authorT.J. CROWDER is a software engineer with 30 years of experience, including over 15 years of professional work in JavaScript. He runs Farsight Software, a software contracting and product company. He's often found helping people on Stack Overflow, where he's a top 10 all-time contributor and the top JavaScript contributor. When not working or writing, he…no, sorry, he's always working or writing – or spending time with his wonderful, supportive wife and fantastic son.Visit us at www.wiley.com for free code samples.Introduction xxxiCHAPTER 1: THE NEW TOYS IN ES2015–ES2020, AND BEYOND 1Definitions, Who’s Who, and Terminology 2What are the “New Toys”? 4How Do New Toys Get Created? 6Keeping Up with the New Toys 9Using Today’s Toys in Yesterday’s Environments, and Tomorrow’s Toys Today 10Review 15CHAPTER 2: BLOCK-SCOPED DECLARATIONS: LET AND CONST 17An Introduction to let and const 18True Block Scope 18Repeated Declarations are an Error 19Hoisting and the Temporal Dead Zone 20A New Kind of Global 22const: Constants for JavaScript 24Block Scope in Loops 26Old Habits to New 36CHAPTER 3: NEW FUNCTION FEATURES 39Arrow Functions and Lexical this, super, etc. 40Default Parameter Values 45“Rest” Parameters 50Trailing Commas in Parameter Lists and Function Calls 52The Function name Property 53Function Declarations in Blocks 55Function Declarations in Blocks: Standard Semantics 57Old Habits to New 60CHAPTER 4: CLASSES 65What is a Class? 66Introducing the New class Syntax 66Comparing with the Older Syntax 75Creating Subclasses 77Leaving Off Object.prototype 97new.target 98class Declarations vs. class Expressions 101More to Come 103Old Habits to New 104CHAPTER 5: NEW OBJECT FEATURES 105Computed Property Names 106Shorthand Properties 107Getting and Setting an Object’s Prototype 107Method Syntax, and super Outside Classes 109Symbol 112New Object Functions 120Symbol.toPrimitive 123Property Order 125Property Spread Syntax 127Old Habits to New 128CHAPTER 6: ITERABLES, ITERATORS, FOR-OF, ITERABLE SPREAD, GENERATORS 131Iterators, Iterables, the for-of Loop, and Iterable Spread Syntax 131Generator Functions 146Old Habits to New 163CHAPTER 7: DESTRUCTURING 165Overview 165Basic Object Destructuring 166Basic Array (and Iterable) Destructuring 169Defaults 170Rest Syntax in Destructuring Patterns 172Using Different Names 173Computed Property Names 174Nested Destructuring 174Parameter Destructuring 175Destructuring in Loops 178Old Habits to New 179CHAPTER 8: PROMISES 181Why Promises? 182Promise Fundamentals 182Using an Existing Promise 186Adding Handlers to Already Settled Promises 201Creating Promises 202Other Promise Utility Methods 207Promise Patterns 210Handle Errors or Return the Promise 210Promises in Series 211Promises in Parallel 213Promise Subclasses 218Old Habits to New 219CHAPTER 9: ASYNCHRONOUS FUNCTIONS, ITERATORS, AND GENERATORS 221async Functions 222async Iterators, Iterables, and Generators 232for-await-of 238Old Habits to New 238CHAPTER 10: TEMPLATES, TAG FUNCTIONS, AND NEW STRING FEATURES 241Template Literals 241Improved Unicode Support 250Iteration 255New String Methods 256Updates to the match, split, search, and replace Methods 259Old Habits to New 260CHAPTER 11: NEW ARRAY FEATURES, TYPED ARRAYS 263New Array Methods 264Iteration, Spread, Destructuring 276Stable Array Sort 276Typed Arrays 277Old Habits to New 292CHAPTER 12: MAPS AND SETS 293Maps 293Sets 300WeakMaps 304WeakSets 314Old Habits to New 316CHAPTER 13: MODULES 319Introduction to Modules 319Module Fundamentals 320Renaming Exports 331Re-Exporting Exports from Another Module 332Renaming Imports 333Importing a Module’s Namespace Object 333Exporting Another Module’s Namespace Object 334Importing a Module Just for Side Effects 335Import and Export Entries 335Imports are Live and Read-Only 338Module Instances are Realm-Specific 340How Modules are Loaded 341Import/Export Syntax Review 348Dynamic Import 350Tree Shaking 357Bundling 359Import Metadata 360Worker Modules 360Old Habits to New 362CHAPTER 14: REFLECTION—REFLECT AND PROXY 365Reflect 365Proxy 371Old Habits to New 395CHAPTER 15: REGULAR EXPRESSION UPDATES 397The Flags Property 398New Flags 398Named Capture Groups 400Lookbehind Assertions 405Unicode Features 408Old Habits to New 413CHAPTER 16: SHARED MEMORY 417Introduction 417Here There Be Dragons! 418Browser Support 418Shared Memory Basics 420Memory is Shared, Not Objects 426Race Conditions, Out-of-Order Stores, Stale Values, Tearing, and More 427The Atomics Object 429Shared Memory Example 434Here There Be Dragons! (Again) 455Old Habits to New 460CHAPTER 17: MISCELLANY 461BigInt 462New Integer Literals 465New Math Methods 467Exponentiation Operator (**) 468Date.prototype.toString Change 470Function.prototype.toString Change 471Number Additions 471Symbol.isConcatSpreadable 474Various Syntax Tweaks 475Various Standard Library / Global Additions 479Annex B: Browser-Only Features 482Tail Call Optimization 488Old Habits to New 491CHAPTER 18: UPCOMING CLASS FEATURES 493Public and Private Class Fields, Methods, and Accessors 493Old Habits to New 514CHAPTER 19: A LOOK AHEAD . . .517Top-Level await 518WeakRefs and Cleanup Callbacks 525RegExp Match Indices 533String.prototype.replaceAll 535Atomics asyncWait 535Various Syntax Tweaks 536Legacy Deprecated RegExp Features 537Thank You for Reading! 538APPENDIX: FANTASTIC FEATURES AND WHERE TO FIND THEM 539Index 557

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