Table Of ContentPaul 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. Where those designations appear in the book, and Manning
Publications was aware of a trademark claim, the designations have been printed in initial caps
or all caps.
Recognizing the importance of preserving what has been written, it is Manning’s policy to have
the books we publish printed on acid-free paper, and we exert our best efforts to that end.
Recognizing also our responsibility to conserve the resources of our planet, Manning books
are printed on paper that is at least 15 percent recycled and processed without the use of
elemental chlorine.
Manning Publications Co. 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
