What Is Underscore?

Underscore.js is a JavaScript library supporting functional programming.

Getting Underscore

The Underscore website has the latest version of the library.

Using Underscore

_.times(4, function() {console.log("Major")});

// (console) Major
// (console) Major
// (console) Major
// (console) Major

var underscore = _.noConflict();

underscore.times(4, function() {console.log("Major")});

// (console) Major
// (console) Major
// (console) Major
// (console) Major

The Source Code for Functional JavaScript

Lemonad library and the official underscore-contrib library

Running the Code in This Book

The source code for Functional JavaScript is available on GitHub.

Notational Conventions

• Avoid assigning variables more than once.
• Do not use eval.
• Do not modify core objects like Array and Function.
• Favor functions over methods.
• If a function is defined at the start of a project, then it should work in subsequent stages as well.
• Functions of zero parameters are used to denote that the arguments don't matter.
• In some examples, ... is used to denote that the surrounding code segments are being ignored.
• Text like inst#method denotes a reference to an instance method.
• I tend to restrict if/else statements to a single line per branch, so I prefer to avoid using curly brackets to wrap the blocks. This saves precious vertical space.
• I like to use semicolons.

Whom Functional JavaScript Is Written For

Anyone looking to learn more about functional programming.

A Roadmap for Functional JavaScript

Chapter 1, Introducing Functional JavaScript
Chapter 2, First-Class Functions and Applicative Programming
Chapter 3, Variable Scope and Closures
Chapter 4, Higher-Order Functions
Chapter 5, Function-Building Functions
Chapter 6, Recursion
Chapter 7, Purity, Immutability, and Policies for Change
Chapter 8, Flow-Based Programming
Chapter 9, Programming Without Class

Conventions Used in This Book

Using Code Examples

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