Hands-On Functional Programming with TypeScript: Explore functional and reactive programming to create robust and testable TypeScript applicatons

273 Pages·2019·1.763 MB·English

by  Remo H. Jansen

Hands-On Functional Programming with TypeScript

Explore functional and reactive programming to create robust and testable
TypeScript applications

Remo H. Jansen
BIRMINGHAM - MUMBAI
Hands-On Functional Programming
with TypeScript
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Commissioning Editor: Richa Tripathi
Acquisition Editor: Denim Pinto
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Technical Editor: Ashi Singh
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First published: January 2019
Production reference: 1290119
Published by Packt Publishing Ltd.
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ISBN 978-1-78883-143-7
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To Lorraine, for being my sword in my victories and my shield in my defeats. Without your support, I
wouldn't be where I am and I wouldn't be the person I am today. Thank you!
– Remo H. Jansen
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Foreword
When TypeScript was officially announced on October 1, 2012, the only docs
available was the dense official language specification. It was not easily
accessible to beginner developers as there was significant focus on syntax.
Additionally, it assumed an existing intimate knowledge of JavaScript.
Nevertheless, it was complete in terms of TypeScript features at the time, and
JavaScript was not as feature-rich as it is today. So, it was a plausible entry point
into TypeScript, and that is what I and many others at the time used to learn
TypeScript.
How times have changed. Over time, TypeScript has gained a number of
features, and so has JavaScript. Keeping up to date now means following
relevant GitHub issues and pull requests on Microsoft/TypeScript and reading up
on the understanding offered by key developers. Remo is one of those key
developers. I got introduced to Remo through his insightful comments on
TypeScript issues and then discovered his blog ( ). Remo's
blog.wolksoftware.com
blog has been a great help in dissecting important features such as JavaScript
decorators and explaining how they are implemented in TypeScript. I find
myself linking fellow developers to his docs instead of the alternatives due to the
high quality of his work.
Not only has Remo been a great help in understanding TypeScript (and
JavaScript), but he has also been a great asset to the TypeScript library
ecosystem. One question that I commonly receive from developers is how to do
dependency injection in TypeScript. My answer is always a direct link to Remo's
extremely useful InversifyJS library ( ).
inversify.io
One of the key concerns that uninformed developers have had about TypeScript
is "it only supports object-oriented programming." That is simply not true.
TypeScript supports all JavaScript paradigms, and functional programming has
first-class support. In fact, it provides a vital piece of famous functional
programming languages (compile-time type information) for JavaScript
developers.
All programming tasks can be considered as simple (data plus data
transformation). This is the mental model encouraged by functional
programming aficionados. To have a deep understanding of functional programs
as a data transform pipeline, you need a way to define your data structures. This
is what is only provided by TypeScript. In the absence of TypeScript, you see
various (somewhat arbitrary) syntax elements used to describe the data structures
that are flowing through your functional programs.
So, if you want to do world-class functional programming and your
programming environment forces you (if only by convenience) to use
JavaScript, please consider TypeScript and know that you are not alone. Remo
H. Jansen is here to help you.

Basarat Ali Syed
Microsoft MVP and one of the leading global references of the TypeScript
community.