Start learning Lodash 4 from this book. Lodash can increase your productivity dramatically in your daily development. It's an essential tool in your JavaScript toolbox. This book talks about Lodash in a systematic way and explains some complicated parts, especially functional programming. This book includes content for Lodash v4.17.21. Lodash - a modern JavaScript utility library delivering modularity, performance and extras. In modern web development, JavaScript is a must-to-learn programming language. Using JavaScript is not an easy task. Most of JavaScript APIs are low-level APIs, which are hard to learn and use. Lodash is a popular JavaScript utility framework. It provides a lot of high-level APIs which are more convenient to remember and use. Developers can dramatically increase productivity by using Lodash. This book is a very good start point to learn Lodash 4 and apply it in practice. It covers core concepts and functions provided by Lodash with real examples. For some complicated functions, e.g. functions related to functional programming, this book has a more detailed explanation.