When comparing two programming languages, there are bound to be structural and grammatical differences. The good news is that both Python and JavaScript are very human-readable languages, so the context switch from Python to JavaScript and Node.js shouldn't be too taxing.
Style is a good question, though: tabs or spaces? Semicolons or not? Many stylistic questions that arise when writing in any programming languages have been answered by the dicta contained within Python's PEP-8 style guide. While JavaScript doesn't have an official style guide, don't worry—it's not the Wild West out there.
Before we can write JavaScript, we must know what it is to be able to read it and understand it. All programming languages vary from one to another, and using your Python knowledge to learn a new language will require a bit of reframing of...