This course does require a basic understanding of Web programming; if you are new to Web programming or need a refresher course, I would highly recommend spending time to go through the following tutorials on W3C:
HTML Tutorials
HTML (HyperText Markup Language) is the most basic building block of the Web. It defines the meaning and structure of web content. Other technologies besides HTML are generally used to describe a web page’s appearance/presentation (CSS) or functionality/behaviour (JavaScript)
Tutorial: https://www.w3schools.com/html
CSS Tutorials
CSS (Cascading Style Sheets) is a style sheet language used for describing the presentation of a document written in a markup language like HTML. CSS is a cornerstone technology of the World Wide Web, alongside HTML and JavaScript.
Tutorial: https://www.w3schools.com/css
JavaScript Tutorials
JavaScript, often abbreviated as JS, is a high-level, just-in-time compiled, multi-paradigm programming language that conforms to the ECMAScript specification. JavaScript has curly-bracket syntax, dynamic typing, prototype-based object-orientation, and first-class functions.
Tutorials: https://www.w3schools.com/js
Object-Oriented JavaScript for Beginners Tutorial
Object-oriented programming (OOP) is a programming language model that organizes software design around data, or objects, rather than functions and logic. An object can be defined as a data field that has unique attributes and behaviour. The Tableau Extension Library is an Object-based library, and therefore you will need to be familiar with these concepts before progressing.
JavaScript Object Basics: https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/Basics
Object-Oriented JavaScript for Beginners: https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/Object-oriented_JS
You can go through the course and copy what I do, however, by understanding these concepts, you will maximise your learning.