Book Image

Professional JavaScript

By : Hugo Di Francesco, Siyuan Gao, Vinicius Isola, Philip Kirkbride
Book Image

Professional JavaScript

By: Hugo Di Francesco, Siyuan Gao, Vinicius Isola, Philip Kirkbride

Overview of this book

In depth knowledge of JavaScript makes it easier to learn a variety of other frameworks, including React, Angular, and related tools and libraries. This book is designed to help you cover the core JavaScript concepts you need to build modern applications. You'll start by learning how to represent an HTML document in the Document Object Model (DOM). Then, you'll combine your knowledge of the DOM and Node.js to create a web scraper for practical situations. As you read through further lessons, you'll create a Node.js-based RESTful API using the Express library for Node.js. You'll also understand how modular designs can be used for better reusability and collaboration with multiple developers on a single project. Later lessons will guide you through building unit tests, which ensure that the core functionality of your program is not affected over time. The book will also demonstrate how constructors, async/await, and events can load your applications quickly and efficiently. Finally, you'll gain useful insights into functional programming concepts such as immutability, pure functions, and higher-order functions. By the end of this book, you'll have the skills you need to tackle any real-world JavaScript development problem using a modern JavaScript approach, both for the client and server sides.
Table of Contents (12 chapters)

Type Checking and Validating the Input Sent to an Endpoint

While type checking and validation are not strictly required for the creation of an API, using them can cut down on debugging time and help to avoid bugs. Having a guaranteed input for an endpoint means that code can be written with a focus on returning the desired result without considering the many edge cases that can be created by input outside that which is expected.

Since this task is so common with the creation of APIs, a library has been created to make verifying the input of Express endpoints easy. With the express-validator middleware, we can simply pass the input requirements to our endpoint as an argument. For example, the requirements described by the JSON object returned in Exercise 18 for our lightbulb's fade action can be represented with the following array:

  check('level').isNumeric().isLength({ min: 0, max: 100 }),