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Mastering Immutable.js

You're reading from   Mastering Immutable.js Better JavaScript development using immutable data

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Product type Paperback
Published in Sep 2017
Publisher Packt
ISBN-13 9781788395113
Length 216 pages
Edition 1st Edition
Languages
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Author (1):
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Adam Boduch Adam Boduch
Author Profile Icon Adam Boduch
Adam Boduch
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Table of Contents (17) Chapters Close

Preface 1. Why Immutable.js? FREE CHAPTER 2. Creating Immutable Data 3. Persistent Changes 4. Filtering Collections and Finding Items 5. Sequences and Side-Effects 6. Sorting Collections 7. Mapping and Reducing 8. Zipping and Flattening 9. Persistent Change Detection 10. Working with Sets 11. Comparing Collections 12. Combining Collections 13. Declarative Decision Making 14. Side-Effects in User Interfaces 15. Side-Effects in Node.js 16. Immutable Architecture

Changing collection values


Once you've added data to your collection, you'll probably need to change it. Lists and maps each have two approaches to change existing values.

Changing list values

Lists can either set a value or update a value. The distinction is subtle, so let's compare the two approaches now.

Setting list values

When you set list values using the set() method, you're changing an existing value. More specifically, you're overwriting the current value at a given index with a new value:

const myList = List.of(1);
const myChangedList = myList.set(0, 2);

console.log('myList', myList.toJS());
// -> myList [ 1 ]
console.log('myChangedList', myChangedList.toJS());
// -> myChangedList [ 2 ]

You're updating the first list value—because the index you're passing to set() is 0—with a value of 2. Using set() like this is a good choice when you know ahead of time what the new value should be. But what about when the new value depends on the current value?

Updating list values

When the new...

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