Now that you have had an introduction to some of the ideas and larger implementations of OOP in JavaScript, please read the following for more detailed explanations.
In addition, you should read the following tutorials on understanding classes and objects in JavaScript. Please note; the syntax and keywords used are different than those you have seen so far. These are for the older, pre-ES6 JavaScript. Everything you read is still valid and will work. However, the way they do the following is differently than you will. You should read the following so as to understand how OOP works in JS.
After reading the above, please also read the following, so you can understand how to use the more modern class syntax. You are expected to use the following for class definitions.