If you're developing in a dynamically-typed language like JavaScript or Python, you may be dearly missing our friend "private" from statically-typed languages like C#, Java, and C++.
I'm sure plenty of developers know about this already, but I feel like no one ever talks about this. In all my years of studying programming, every time I've searched for how to achieve true encapsulation in JavaScript, the same answer always appears:
You can't.