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

Maintaining sort order


If your application has collections that are always sorted, then you need a way to maintain that sort order. This means that once you add or change values in a collection, you have to make sure that the collection is still in the order that you expected.

Finding the insertion index

Let's say that you want to add a value to a list that's already sorted. Using push() will insert the value at the end of the list, and this isn't what you want. The insert() method can put the value at a particular index—you just have to figure out which index to use to keep the list sorted:

const sortedInsert = (item, list) => {
  let low = 0;
  let high = list.count();

  while (low < high) {
    const mid = (low + high) >>> 1;
    if (item > list.get(mid)) {
      low = mid + 1;
    } else {
      high = mid;
    }
  }
  return list.insert(low, item);
};

The sortedIndex() function takes a value and a list into which to insert the value as arguments. It then does a simple...