If you really want to learn anything, not just programming or any programming language, you can do so in a relatively fast way.
However, before you start learning anything, please remember that you can't know everything at once or in just one day.
Now, let's come to the solution. JavaScript is often used to manipulate and enhance web pages. I assume that you are already familiar with HTML and CSS. If you are not familiar with HTML and CSS, you can visit W3Schools.com to gain an understanding of them.
The easiest way to start learning is to begin with the 10% of the programming language that is used 70 to 80% of the time. Learning JavaScript, like any programming language, requires practice to become proficient. You won't become proficient in just a few days, but starting with this initial 10% can help you become really good at learning any programming language, not just JavaScript."
Variables and Data Types
Operators
Control Structures
Functions
Objects
Arrays
Event Handling
DOM Manipulation
Asynchronous JavaScript
Modules
JSON
ES6 Features
Regular Expressions
Promises and Async/Await
Remember that the specific topics you must focus on may vary depending on your project or job requirements. However, a strong understanding of these fundamental concepts will provide a solid foundation for JavaScript development and cover a significant portion of what you'll encounter in real-world coding tasks.