Lo-Dash Essentials

Adam Boduch

• Publisher: Packt Publishing
• Year: 2015
• ISBN:
  9781784398330
• Topic: Computer Science
• Subtopic: Programming in JavaScript
• Index: Computer Science

Lo-Dash Essentials

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Table of Contents

Lo-Dash Essentials

Credits

About the Author

About the Reviewers

www.PacktPub.com

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Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. Working with Arrays and Collections

The difference between arrays and collections

Iterating over collections

Sorting data

Using sortBy()

Maintaining the sort order

Searching for data

Filtering collections

Finding items in collections

Slicing collections into smaller pieces

First and last collection portions

Splitting collections into chunks

Building unique arrays

Transforming collections

Grouping collection items

Counting collection items

Flattening and compacting

Validating some or all items

Unions, intersections, and differences

Summary

2. Working with Objects

Determining an object type

Type coercion

Managing function arguments

Arithmetic

Callable objects

Assigning and accessing properties

Extending objects

Defaults for new objects

Finding keys and values

Iterating over objects

Basic For Each

Including inherited properties

Keys and values

Calling methods

Getting results

Finding methods

Transforming objects

Using pairs

Picking and omitting properties

Inverting keys and values

Creating and cloning objects

Creating objects

Cloning objects

Summary

3. Working with Functions

Binding function contexts

Changing the this keyword

Binding methods

Dynamic methods

Decorating functions

Partials

Function decorators

Function constraints

Limiting call counts

Caching values

Timed execution

Delaying function calls

Deferring function calls

Throttling function calls

Debouncing function calls

Composing and currying functions

Composing functions

Currying functions

Summary

4. Transformations Using Map/Reduce

Plucking values

Mapping collections

Including and excluding properties

Performing calculations

Calling functions

Filtering and mapping

Mapping objects

Working with keys

Calling methods

Mapping key-value pairs

Reducing collections

Summing values

Filtering and reducing

Min, max, and average operations

Reducing objects

Reducing keys

Object accumulators

Binding contexts

Map/reduce patterns

Generic callback functions

Map/reduce chains

Summary

5. Assembling Chains

Creating Lo-Dash wrappers

Chained calls

Wrapping values

Explicit and implicit chaining

Building filters

Multiple filter() calls

Combining filter() with where()

Dropping and taking collection items

Rejecting items

Using initial() and rest()

Testing truth conditions

Testing if a collection contains an item

Everything or anything is true

Counting items

Using length and size()

Grouping using countBy()

Reducing collections

Transformations

Building groups, unions, and unique values

Plucking values

Creating arrays using without()

Finding the min and max values

Finding the index

Using difference() and xor()

Intermediary results

Tapping into chains

Injecting values

Keys and values

Filtered keys and values

Omitting and picking properties

Returning wrappers

Summary

6. Application Building Blocks

Generic functions

Specific functions

Generic function arguments

Using partials

Generic callbacks

Generic wrappers and chains

Generic filters

Returning chains

Composing functions

Composing generic functions

Composing callbacks

Composing chains

Method composition

Creating mixins

Creating an average() function

Creating a distance() function

Summary

7. Using Lo-Dash with Other Libraries

Modules

Organizing your code with modules

Requiring Lo-Dash

Working with Lo-Dash AMD modules

jQuery

Challenges faced by Lo-Dash

Challenges faced by jQuery

Using jQuery instances as collections

Binding functions

Working with jQuery deferred instances

Backbone

Replacing Underscore.js

Full-featured Lo-Dash and Backbone

Enhancing collections and models

Node.js

Installing the Lo-Dash package

Creating a simple command

Custom Lo-Dash builds

Summary

8. Internal Design and Performance

Design principles

Function compilation to base functions

Optimizing for the common case

Loops are simple

Callbacks and function binding

Improving performance

Changing the operation order

Sorting and indexing collections

Bound and unbound callbacks

Lazy evaluation

Caching things

Summary

Index

Lo-Dash Essentials

Copyright © 2015 Packt Publishing

All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, without the prior written permission of the publisher, except in the case of brief quotations embedded in critical articles or reviews.

Every effort has been made in the preparation of this book to ensure the accuracy of the information presented. However, the information contained in this book is sold without warranty, either express or implied. Neither the author, nor Packt Publishing, and its dealers and distributors will be held liable for any damages caused or alleged to be caused directly or indirectly by this book.

Packt Publishing has endeavored to provide trademark information about all of the companies and products mentioned in this book by the appropriate use of capitals. However, Packt Publishing cannot guarantee the accuracy of this information.

First published: January 2015

Production reference: 1210115

Published by Packt Publishing Ltd.

Livery Place

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Birmingham B3 2PB, UK.

ISBN 978-1-78439-833-0

www.packtpub.com

Credits

Author

Adam Boduch

Reviewers

Joe Grund

Richard Hubers

Tyler Morgan

Francois-Guillaume Ribreau

Matt Traynham

Commissioning Editor

Dipika Gaonkar

Acquisition Editor

Meeta Rajani

Content Development Editor

Pooja Nair

Technical Editor

Mrunal M. Chavan

Copy Editors

Vikrant Phadkay

Rashmi Sawant

Project Coordinator

Suzanne Coutinho

Proofreaders

Kevin McGowan

Ameesha Green

Lucy Rowland

Indexers

Priya Sane

Tejal Soni

Production Coordinator

Komal Ramchandani

Cover Work

Komal Ramchandani

About the Author

Adam Boduch is a senior frontend engineer from Toronto. He currently works on delivering innovative products at Virtustream. Adam loves tinkering with the latest JavaScript libraries and is passionate about high-performance user interfaces.

Having focused on writing about jQuery in jQuery UI Themes Beginner's Guide and jQuery UI Cookbook, both by Packt Publishing, Adam has ventured into a new territory with this title, Lo-Dash Essentials. He is an avid proponent of Backbone and the ecosystem that surrounds it.

About the Reviewers

Joe Grund is a full-stack software engineer. He has written numerous rich applications utilizing the latest technologies and methodologies. Joe enjoys writing terse JavaScript code in a functional style and building real-time systems. He works at Intel, where he uses JavaScript to solve interesting problems. He lives in Orlando and can be found on Twitter (@joegrund), GitHub (jgrund), and his blog (joegrund.com), where he muses about building complex systems out of simple functional primitives.

I would like to thank my wife, Sunshine, and my three awesome kids, Luke, Lilly, and Michael, for their love and support.

Richard Hubers is an all-round web developer with more than 15 years of experience. He likes writing web apps and APIs in JavaScript and .NET, and learning the newest and latest technologies. He lives and works in Amsterdam.

Tyler Morgan is a renowned Ruby developer. He loves the JavaScript landscape, especially Node.js. He is an instructor of an intensive full-stack JavaScript development course at Code Fellows, located in Seattle, Washington.

Francois-Guillaume Ribreau is a full-stack developer and Frenc...