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

Mapping lists of maps


Lists of maps are common in Immutable.js applications. Also common is the need to map these lists to lists of simple values. This means taking a simple value from the map, or using the map to compute a simple value.

Plucking values

Plucking a value from a map is another way of saying look up a value based on a key. It's common to say "pluck" when mapping a collection of maps to a particular key. Imagine plucking blades of grass from a lawn that fit a particular profile. Let's look at an example:

const myList = List.of(
  Map.of('first', 1, 'second', 2),
  Map.of('first', 3, 'second', 4),
  Map.of('first', 5, 'second', 6)
);
const myMappedList = myList
  .map(v => v.get('second'));

console.log('myList', myList.toJS());
// -> myList [ { first: 1, second: 2 },
// ->          { first: 3, second: 4 },
// ->          { first: 5, second: 6 } ]
console.log('myMappedList', myMappedList.toJS());
// -> myMappedList [ 2, 4, 6 ]

The myMappedList list now has the values...