There is lot of content on the internet to get a good understanding of Javascript fundamentals. But one of the most valuable resources I found was a course by Kyle Simpson(getify) named "You Don't know JS". He is a great teacher. He especially focuses on explaining the fundamental concepts very clearly. He has also written a book series with the same name, which you can access for free on GitHub. GitHub - getify/You-Dont-Know-JS: A book series on JavaScript. @YDKJS on twitter.

Another useful resource to grasp how JavaScript handles single threaded, non-blocking IO, you can checkout a video by Philip Roberts titled What the heck is the event loop anyway where he visually explains what happens under the hood when we run Javascript code.

I hope this helps. If you have any specific questions or topics that you want to learn more about, feel free to contact me.

1. Start with a good tutorial or course. There are many great resources available online and in libraries. Choose one that is well-written and easy to follow.
2. Focus on the basics. Don't try to learn too much too quickly. Start with the basics, such as variables, data types, operators, control flow, and functions.
3. Write code. The best way to learn how to code is to practice writing code. Try to write code every day, even if it's just for a few minutes.
4. Use a debugger. A debugger is a tool that allows you to step through your code line by line and inspect the values of variables. This can be very helpful for debugging your code and understanding how it works.
5. Find a mentor or community. If you're stuck, don't be afraid to ask for help. There are many online communities and forums where you can ask questions and get help from other JavaScript developers.

Here are some specific topics that you should focus on when learning the core JavaScript fundamentals:

• Variables and data types: Variables are used to store data, and data types specify what kind of data can be stored in a variable.
• Operators: Operators are used to perform operations on data, such as arithmetic, logical, and relational operations.
• Control flow: Control flow statements allow you to control the execution of your code, such as using if statements, loops, and switch statements.
• Functions: Functions are reusable blocks of code that can be used to perform specific tasks.
• Objects: Objects are data structures that can store properties and methods.
• Arrays: Arrays are data structures that can store a collection of items.

Once you have a good understanding of the core JavaScript fundamentals, you can start to learn more advanced topics, such as asynchronous programming, object-oriented programming, and event handling.

Here are some additional tips for grasping core JavaScript fundamentals:

• Use a consistent code editor or IDE. This will help you to learn the shortcuts and features of your chosen development environment.
• Read JavaScript code regularly. This will help you to see how other developers write JavaScript code and to learn new techniques.
• Contribute to open-source projects. This is a great way to get experience working with other developers and to learn from their code.

Learning JavaScript can be challenging, but it is also very rewarding. With hard work and dedication, you can learn the core JavaScript fundamentals and become a competent JavaScript developer.