At times, JavaScript can be a frustrating programming language to work with. Just when you think you have it entirely figured out, performance or cross-browser issues reveal themselves in the worst possible way. Lo-Dash is just one of many libraries that aim to help JavaScript programmers write code that's elegant, efficient, and portable. Underscore.js introduced a better way to perform functional programming with JavaScript. Lo-Dash is a continuation of this effort, and throughout this book, we'll see what sets Lo-Dash apart from other libraries out there, including Underscore.
At its heart, JavaScript is a functional language, but not necessarily a pure functional language—you can modify variables and introduce side effects. However, functions are first-class citizens and you can do a lot with them. Lo-Dash embraces this idea and gives programmers all the tools they need to write functional code that's readable and maintainable. All the cool things you can do with higher-order functions in other languages are possible with Lo-Dash as well.
It's not just the low-level utilities and performance gains that Lo-Dash delivers, though these are always welcome; it's also the enhanced programming model and the ideas that Lo-Dash borrows from other languages such as functional and applicative programming. These are imparted to JavaScript applications as a coherent API. Underscore got the ball rolling, and Lo-Dash further enhances these ideas, albeit using different design and implementation strategies.
Chapter 1, Working with Arrays and Collections, explains that collections are similar to arrays but are more general than arrays. This chapter looks at the differences between these two constructs and the available Lo-Dash functions that operate on them.
Chapter 2, Working with Objects, teaches you how Lo-Dash treats objects as collections. This chapter looks at the available functions that work with objects.
Chapter 3, Working with Functions, focuses on the functional tools provided by Lo-Dash.
Chapter 4, Transformations Using Map/Reduce, explains that the map/reduce programming model is used often in the Lo-Dash code. This chapter offers many examples that utilize the Lo-Dash map/reduce tools in their various forms.
Chapter 5, Assembling Chains, explains how Lo-Dash can chain together functions that operate on a value. This chapter explores what chains are and how they work.
Chapter 6, Application Building Blocks, looks at the high-level application components that help organize the Lo-Dash code.
Chapter 7, Using Lo-Dash with Other Libraries, explains that Lo-Dash doesn't do everything. This chapter uses examples to illustrate where other libraries can help Lo-Dash and vice versa.
Chapter 8, Internal Design and Performance, looks at some of the internal design decisions of Lo-Dash and provides some advice on how to improve the performance of your Lo-Dash code.
The only software required for running the examples in this book is a modern web browser. All JavaScript libraries are packaged with the code samples. The only exception is Chapter 7, Using Lo-Dash with Other Libraries, which involves working with Node.js (http://nodejs.org/) and some corresponding npm packages.
This book is for the intermediate JavaScript programmer who is either new to Lo-Dash or has been using it for a while. Whether you've never written a line of Lo-Dash or you've got Lo-Dash code running in production, this book has something for you. Ideally, you've written some intermediate/advanced JavaScript code and utilized libraries such as jQuery or Backbone.
In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and explanations of their meanings.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "The union() function concatenates collections, with duplicate values removed."
A block of code is set as follows:
var collection = [
{ name: 'Jonathan' },
{ first: 'Janet' },
{ name: 'Kevin' },
{ name: 'Ruby' }
];
if (!_.every(collection, 'name')) {
return 'Missing name property';
}
// → "Missing name property"Any command-line input or output is written as follows:
npm install -g grunt-cli grunt-contrib-connect
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