Table Of Content

Paul P. Daniels Luis Atencio F Ben Lesh OREWORD BY M A N N I N G RxJS in Action RxJS in Action COVERS RXJS 5 PAUL P. DANIELS LUIS ATENCIO FOREWORD BY BEN LESH MANNING SHELTER ISLAND For online information and ordering of this and other Manning books, please visit www.manning.com. The publisher offers discounts on this book when ordered in quantity. For more information, please contact Special Sales Department Manning Publications Co. 20 Baldwin Road PO Box 761 Shelter Island, NY 11964 Email: [email protected] ©2017 by Manning Publications Co. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by means electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. 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Development editor: Frances Lefkowitz 20 Baldwin Road Technical development editor: Dean Iverson PO Box 761 Project editor: Janet Vail Shelter Island, NY 11964 Copyeditor: Linda Recktenwald Proofreader: KatieTennant Technical proofreader: Cody Sand Typesetter: Dottie Marsico Cover designer: Marija Tudor ISBN 9781617293412 Printed in the United States of America 1 2 3 4 5 6 7 8 9 10 – EBM – 22 21 20 19 18 17 brief contents PART 1 UNDERSTANDING STREAMS 1 1 ■ Thinking reactively 3 2 ■ Reacting with RxJS 28 3 ■ Core operators 61 4 ■ It’s about time you used RxJS 85 PART 2 OBSERVABLES IN PRACTICE 119 5 ■ Applied reactive streams 121 6 ■ Coordinating business processes 151 7 ■ Error handling with RxJS 182 PART 3 MASTERING RXJS 209 8 ■ Heating up observables 211 9 ■ Toward testable, reactive programs 245 10 ■ RxJS in the wild 271 v contents foreword xiii preface xv acknowledgments xvii about this book xix about the authors xxiv about the cover xxv PART 1 UNDERSTANDING STREAMS.................................1 1 Thinking reactively 3 1.1 Synchronous vs. asynchronous computing 5 Issues with blocking code 5 ■ Non-blocking code with callback functions 6 ■ Understanding time and space 7 Are callbacks out of the picture? 9 ■ Event emitters 11 1.2 Better callbacks with Promises 12 1.3 The need for a different paradigm 14 1.4 The Reactive Extensions for JavaScript 17 Thinking in streams: data flows and propagation 17 Introducing the RxJS project 18 ■ Everything is a stream 19 ■ Abstracting the notion of time from your programs 21 ■ Components of an Rx stream 23 1.5 Reactive and other programming paradigms 26 1.6 Summary 27 vii viii CONTENTS 2 Reacting with RxJS 28 2.1 Functional programming as the pillar of reactive programming 29 Functional programming 30 ■ The iterator pattern 38 2.2 Stream’s data-driven approach 41 2.3 Wrapping data sources with Rx.Observable 43 Identifying different sources of data 43 ■ Creating RxJS observables 44 ■ When and where to use RxJS 46 To push or not to push 49 2.4 Consuming data with observers 53 The Observer API 53 ■ Creating bare observables 55 Observable modules 57 2.5 Summary 60 3 Core operators 61 3.1 Evaluating and cancelling streams 62 Downside of eager allocation 62 ■ Lazy allocation and subscribing to observables 64 ■ Disposing of subscriptions: explicit cancellation 65 ■ Cancellation mismatch between RxJS and other APIs 67 3.2 Popular RxJS observable operators 69 Introducing the core operators 70 3.3 Sequencing operator pipelines with aggregates 77 Self-contained pipelines and referential transparency 77 Performance advantages of sequencing with RxJS 80 3.4 Summary 83 4 It’s about time you used RxJS 85 4.1 Why worry about time? 87 4.2 Understanding asynchronous timing with JavaScript 88 Implicit timing 88 ■ Explicit timing 88 ■ The JavaScript timing interfaces 90 4.3 Back to the future with RxJS 94 Propagation 98 ■ Sequential time 99 4.4 Handling user input 101 Debouncing 101 ■ Throttling 108 4.5 Buffering in RxJS 111 4.6 Summary 116 CONTENTS ix PART 2 OBSERVABLES IN PRACTICE ............................119 5 Applied reactive streams 121 5.1 One for all, and all for one! 122 Interleave events by merging streams 124 ■ Preserve order of events by concatenating streams 130 ■ Switch to the latest observable data 133 5.2 Unwinding nested observables: the case of mergeMap 135 5.3 Mastering asynchronous streams 141 5.4 Drag and drop with concatMap 146 5.5 Summary 150 6 Coordinating business processes 151 6.1 Hooking into the observable lifecycle 152 Web hooks and the observer pattern 153 Hooked on observables 154 6.2 Joining parallel streams with combineLatest and forkJoin 159 Limitations of using Promises 162 ■ Combining parallel streams 163 ■ More coordination with forkJoin 168 6.3 Building a reactive database 170 Populating a database reactively 172 ■ Writing bulk data 175 ■ Joining related database operations 177 ■ Reactive databases 180 6.4 Summary 181 7 Error handling with RxJS 182 7.1 Common error-handling techniques 183 Error handling with try/catch 183 ■ Delegating errors to callbacks 184 ■ Errors and Promises 186 7.2 Incompatibilities between imperative error-handling techniques and functional and reactive code bases 188 7.3 Understanding the functional error-handling approach 189 7.4 The RxJS way of dealing with failure 193 Errors propagated downstream to observers 193 Catching and reacting to errors 195 ■ Retrying failed