Functional-Light JavaScript : Balanced, Pragmatic FP in JavaScript

Functional-Light JavaScript is a balanced, pragmatic exploration of Functional Programming in JavaScript.Functional Programming (FP) is an incredibly powerful paradigm for structuring code that yields more robust, verifiable, and readable programs. If you've ever tried to learn FP but struggled with terms like "monad", mathematical concepts like category theory, or symbols like (lambda), you're not alone.Functional-Light programming distills the most vital aspects of FP—function purity, value immutability, composition, and more!—down to approachable JavaScript patterns. Rather than the all-or-nothing dogmatism often encountered in FP, this book teaches you how to improve your programs line by line. Table of Contents 5 Foreword 9 Preface 11 Mission 12 Chapter 1: Why Functional Programming? 14 At a Glance 15 Confidence 17 Communication 18 Readability 20 Perspective 22 How to Find Balance 23 Resources 24 Summary 26 Chapter 2: The Nature Of Functions 27 What Is a Function? 27 Function Input 29 Named Arguments 38 Function Output 40 Functions of Functions 46 Syntax 52 What's This? 60 Summary 63 Chapter 3: Managing Function Inputs 65 All for One 65 Adapting Arguments to Parameters 70 Some Now, Some Later 73 One at a Time 82 Order Matters 93 No Points 98 Summary 104 Chapter 4: Composing Functions 105 Output to Input 105 General Composition 112 Reordered Composition 120 Abstraction 122 Revisiting Points 129 Summary 134 Chapter 5: Reducing Side Effects 135 Effects on the Side, Please 135 Once Is Enough, Thanks 145 Pure Bliss 150 There or Not 157 Purifying 163 Summary 172 Chapter 6: Value Immutability 173 Primitive Immutability 173 Value to Value 175 Reassignment 178 Performance 184 Treatment 187 Summary 190 Chapter 7: Closure vs. Object 191 The Same Page 192 Look Alike 193 Two Roads Diverged in a Wood... 204 Summary 215 Chapter 8: Recursion 217 Definition 218 Declarative Recursion 225 Stack 228 Rearranging Recursion 234 Summary 243 Chapter 9: List Operations 245 Non-FP List Processing 246 Map 246 Filter 253 Reduce 257 Advanced List Operations 265 Method vs. Standalone 273 Looking for Lists 280 Fusion 283 Beyond Lists 286 Summary 296 Chapter 10: Functional Async 297 Time as State 297 Eager vs. Lazy 300 Reactive FP 301 Summary 309 Chapter 11: Putting It All Together 311 Setup 311 Stock Events 313 Stock Ticker UI 316 Summary 328 Appendix A: Transducing 330 Why, First 330 How, Next 333 What, Finally 347 Summary 350 Appendix B: The Humble Monad 351 Type 352 Loose Interface 352 Just a Monad 353 Maybe 358 Humble 361 Summary 365 Appendix C: FP Libraries 366 Stuff to Investigate 366 Ramda (0.23.0) 367 Lodash/fp (4.17.4) 369 Mori (0.3.2) 369 Bonus: FPO 371 Bonus #2: fasy 373 Summary 376