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)

10. Functional Programming with JavaScript

Activity 15: onCheckout Callback Prop


  1. Change the current directory to Lesson10 and run npm install if you haven't done so in this directory before. npm install downloads the dependencies that are required in order to run this activity (React and Parcel).
  2. Run parcel serve activity-on-checkout-prop-start.html and then execute npm run Activity15. You will see the application starting up, as follows:

    Figure 10.42: Output after running the start html script
  3. Go to http://localhost:1234 (or whichever URL the start script output). You should see the following HTML page:
    Figure 10.43: Initial application in the browser
  4. The onClick of the Proceed to checkout can be implemented as follows:
      render() {
        return (
            <p>You have {this.state.items.length} items in your basket</p>