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Table Of Contents

Mastering Immutable.js

By : Adam Boduch

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.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

Why Immutable.js?

Why Immutable.js?

Mutations are destructive

The Immutable.js approach

Unidirectional data flow

Other libraries similar to Immutable.js

Summary

Creating Immutable Data

Creating Immutable Data

Immutable.js constructors

Using the of() method

Parsing data using the fromJS() function

Summary

Persistent Changes

Persistent Changes

Adding values to collections

Changing collection values

Removing values from collections

Emptying collections

Keeping track of changes

Summary

Filtering Collections and Finding Items

Filtering Collections and Finding Items

Filtering using simple comparisons

Filtering maps by keys

Finding collection values

Filtering using deep equality

Partial matches

Changing the search direction

Summary

Sequences and Side-Effects

Sequences and Side-Effects

Why lazy evaluation?

Sequence creation and iteration

Lazy filtering

Limiting results and reducing work

Summary

Sorting Collections

Sorting Collections

Sorting and reversing

Sorting lists of maps

Ordered maps

Sorting maps

Maintaining sort order

Summary

Mapping and Reducing

Mapping and Reducing

Mapping lists of maps

Mapping to new lists of maps

Reducing collections

Lazy mapping

Summary

Zipping and Flattening

Zipping and Flattening

Zipping collections

Flattening collections

Summary

Persistent Change Detection

Persistent Change Detection

Collection equality

Transformations versus mutations

Caching side-effects

Summary

Working with Sets

Working with Sets

Sets are not lists

Removing duplicates

Ordered sets

Maintaining sets

Summary

Comparing Collections

Comparing Collections

Set intersections

List intersections

Collection differences

Comparing maps

Subsets and supersets

Summary

Combining Collections

Combining Collections

Merging maps

Merging lists

Concatenating lists and sequences

Interposing and interleaving

Summary

Declarative Decision Making

Declarative Decision Making

Mapping behavior

Parameters and defaults

Composing behavior

Summary

Side-Effects in User Interfaces

Side-Effects in User Interfaces

A simple application

DOM side-effects

React side-effects

Summary

Side-Effects in Node.js

Side-Effects in Node.js

Reading data into collections

Writing collection data

Summary

Immutable Architecture

Immutable Architecture

The reusable application state updater

Initial application state

Events and state updaters

Executing side-effects

Summary

Sorting lists of maps

You've seen how to use the sortBy() method to negate a value so that you can sort in descending order. The sortBy() method is also useful when you need to sort by more complex data and sort criteria. Even the sortBy() method has its limitations with respect to sorting lists of maps; so, you have to think about alternative approaches here.

The sortBy() method

The sortBy() method uses the default greater than and less than comparator function—the same default used by sort(). The function that is passed to sortBy() is called an iteratee, which is a function that's used to produce values that are fed into the comparator function. This is useful when you want to use the default comparator—writing iteratees is easier than customizing comparator functions.

Note

If it turns out that you've written an iteratee function and you have a reusable comparator function, you can use both. The sortBy() method accepts a comparator as its second argument.

Let's start by writing a simple utility...

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Tech Concepts

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Programming languages

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