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)

1. JavaScript, HTML, and the DOM

Activity 1: Extracting Data from a Page


  1. Initialize a variable to store the entire content of the CSV:
    var csv = 'name,price,unit\n';
  2. Query the DOM to find all the elements that represent each product. Notice how we wrap the HTMLCollection instance returned in Array.from so that we can handle it like a normal array:
    var elements = Array.from(document.getElementsByClassName('item'));
  3. Iterate over each element found:
    elements.forEach((el) => {});
  4. Inside the closure, using the product element, query to find the price with the unit. Split the string using a slash:
    var priceAndUnitElement = el.getElementsByTagName('span')[0];
    var priceAndUnit = priceAndUnitElement.textContent.split("/");
    var price = priceAndUnit[0].trim();
    var unit = priceAndUnit[1].trim();
  5. Then query for the name:
    var name = el.getElementsByTagName('a')[0].textContent;
  6. Append all information to the variable...