Book Image

Mastering Immutable.js

By : Adam Boduch
Book Image

Mastering Immutable.js

By: Adam Boduch

Overview of this book

Immutable.js is a JavaScript library that will improve the robustness and dependability of your larger JavaScript projects. All aspects of the Immutable.js framework are covered in this book, and common JavaScript situations are examined in a hands-on way so that you gain practical experience using Immutable.js that you can apply across your own JavaScript projects. The key to building robust JavaScript applications using immutability is to control how data flows through your application, and how the side-effects of these flows are managed. Many problems that are difficult to pinpoint in large codebases stem from data that’s been mutated where it shouldn’t have been. With immutable data, you rule out an entire class of bugs. Mastering Immutable.js takes a practical, hands-on approach throughout, and shows you the ins and outs of the Immutable.js framework so that you can confidently build successful and dependable JavaScript projects.
Table of Contents (23 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface

Concatenating lists and sequences


If you have several lists that you need to run through a side-effect, it's usually a good choice to concatenate these lists together. It's easier for side-effects to iterate over one collection than several of them.

Simple value concatenation

The best way to think about concatenating lists together is as basic addition. You're effectively adding lists together, resulting in a larger list. You use the concat() method to concatenate lists:

const myList1 = List.of(1, 2, 3);
const myList2 = List.of(4, 5, 6);
const myList3 = List.of(7, 8, 9);
const myCombinedList = myList1.concat(
  myList2,
  myList3
);

console.log('myList1', myList1.toJS());
// -> myList1 [ 1, 2, 3 ]
console.log('myList2', myList2.toJS());
// -> myList2 [ 4, 5, 6 ]
console.log('myList3', myList3.toJS());
// -> myList3 [ 7, 8, 9 ]
console.log('myCombinedList', myCombinedList.toJS());
// -> myCombinedList [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]

Now our side-effect only needs to worry about iterating...