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  • Book Overview & Buying Lo-Dash Essentials
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Lo-Dash Essentials

Lo-Dash Essentials

By : Adam Boduch
4.8 (8)
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Lo-Dash Essentials

Lo-Dash Essentials

4.8 (8)
By: Adam Boduch
Buy this Book

Overview of this book

If you are a curious JavaScript developer interested simultaneously in tweaking the efficiency of your code, as well as improving the conciseness of it, and maintaining the readability of it, then this is the book for you. Ideally, the book is intended for readers already working on JavaScript projects and using frameworks such as jQuery and Backbone. Even if you're already using Lo-Dash, this book will show you how to use it efficiently. While extensive JavaScript experience isn't a requirement, you should have at least some prior programming experience in order to best understand the concepts presented.
Table of Contents (10 chapters)
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Preface
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Preface
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What this book covers
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What you need for this book
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Who this book is for
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Conventions
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Reader feedback
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Customer support
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1
1. Working with Arrays and Collections
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1. Working with Arrays and Collections
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The difference between arrays and collections
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Iterating over collections
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Sorting data
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Searching for data
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Slicing collections into smaller pieces
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Transforming collections
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Summary
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2. Working with Objects
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2. Working with Objects
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Determining an object type
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Assigning and accessing properties
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Iterating over objects
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Calling methods
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Transforming objects
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Creating and cloning objects
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Summary
3
3. Working with Functions
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3. Working with Functions
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Binding function contexts
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Decorating functions
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Function constraints
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Timed execution
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Composing and currying functions
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Summary
4
4. Transformations Using Map/Reduce
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4. Transformations Using Map/Reduce
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Plucking values
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Mapping collections
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Mapping objects
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Reducing collections
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Reducing objects
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Binding contexts
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Map/reduce patterns
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Summary
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5. Assembling Chains
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5. Assembling Chains
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Creating Lo-Dash wrappers
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Building filters
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Testing truth conditions
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Counting items
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Transformations
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Intermediary results
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Keys and values
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Returning wrappers
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Summary
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6. Application Building Blocks
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6. Application Building Blocks
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Generic functions
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Generic wrappers and chains
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Composing functions
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Creating mixins
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Summary
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7. Using Lo-Dash with Other Libraries
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7. Using Lo-Dash with Other Libraries
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Modules
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jQuery
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Backbone
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Node.js
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Summary
8
8. Internal Design and Performance
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8. Internal Design and Performance
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Design principles
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Improving performance
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Lazy evaluation
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Caching things
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Summary
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Index
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Index

Lazy evaluation

With the introduction of Lo-Dash 3.0, some functions use a lazy evaluation to compute their results. This simply means that the items in a given collection aren't iterated over until they're actually needed. It's figuring out when they're needed that is the tricky part. For example, just calling a single Lo-Dash function doesn't invoke any lazy evaluation mechanism. However, operations that are chained together could certainly benefit from this approach, in certain circumstances. For example, when we're only taking 10 items from the result, there's no need to iterate over the entire collection further up the chain.

To get an idea of what a lazy evaluation looks like, let's write some code to utilize it. There's nothing explicit to be done. The lazy mechanism happens transparently, behind the scenes, depending on which operations make up our chain and what order they're called in:

var collection = _.range(10);

_(collection)
    .reject(function(item) {
        console.log(...
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Tech Concepts
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Programming languages
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Lo-Dash Essentials
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