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Mastering JavaScript Functional Programming

You're reading from   Mastering JavaScript Functional Programming In-depth guide for writing robust and maintainable JavaScript code in ES8 and beyond

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Product type Paperback
Published in Nov 2017
Publisher Packt
ISBN-13 9781787287440
Length 386 pages
Edition 1st Edition
Languages
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Author (1):
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Federico Kereki Federico Kereki
Author Profile Icon Federico Kereki
Federico Kereki
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Table of Contents (15) Chapters Close

Preface 1. Becoming Functional - Several Questions 2. Thinking Functionally - A First Example FREE CHAPTER 3. Starting Out with Functions - A Core Concept 4. Behaving Properly - Pure Functions 5. Programming Declaratively - A Better Style 6. Producing Functions - Higher-Order Functions 7. Transforming Functions - Currying and Partial Application 8. Connecting Functions - Pipelining and Composition 9. Designing Functions - Recursion 10. Ensuring Purity - Immutability 11. Implementing Design Patterns - The Functional Way 12. Building Better Containers - Functional Data Types 13. Bibliography
14. Answers to Questions

Pure functions

Pure functions behave in the same way as mathematical functions and provide diverse benefits. A function may be considered to be pure if it satisfies two conditions:

  • Given the same arguments, the function always calculates and returns the same result, no matter how many times it's invoked, or in which conditions you call it. This result value cannot depend on any outside information or state, which could change during the program execution, and cause it to return a different value. Nor can the function result depend on I/O results, random numbers, or some other external variable, not directly controllable, value.
  • When calculating its result, the function doesn't cause any observable side effect, including output to I/O devices, mutation of objects, change to program state outside of the function, and so on.

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