One of the big leaps you'll have to make as a JavaScript developer is wrapping your head around Object Oriented Programming (OOP). This is tough, and that's ok because it's tough for everyone at first. When you start out with JavaScript you're taught to use functions as your primary way of organizing your code. This is fine, but you'll probably find that organizing your code around objects makes larger projects easier to accomplish and improve / maintain.
The cool thing is that what OOP amounts to is an organizational strategy. I have a set of related tasks, how do I go about starting the project and organizing my code? These tasks have some variables and functions that are used to accomplish them, so you create them and write the logic for them to interact. While you can write those out as detached functions and variables, making those variables and functions into properties and methods of an object can make the division between those tasks easier to see and maintain.
Maint