Is there a javascript fundamentals course?

Here is a playlist of concepts every Javascript developer must be familiar with. It is updated regularly.

There are quite a few options for you once master the basics of javascript. Here are a few courses that are highly recommended

Beginner:

Data Structures and Algorithms in JavaScript
Algorithms in JavaScript

Understand JavaScript Arrays
Reduce Data with Javascript Array#reduce
Understand JavaScript's this Keyword in Dept

Intermediate:

Quickly Transform Data with Transducers
Advanced Logging with the JavaScript Console
Learn ES6 (ECMAScript 2015)

Advanced:

Professor Frisby Introduces Composable Functional JavaScript
Asynchronous Programming: The End of The Loop

Async:

JavaScript Promises in Depth
Asynchronous JavaScript with async/await
Write simple asynchronous code with JavaScript generators

There are quite a few websites where you can test your new found skills as well. Practice is the key to maintaining them. exercism.io is one of these websites. Check it out and have fun with the coding problems!