How are your basics? If you are a logical person with quick learning capacities, you can jump straight into it. Just don't forget to spend some time to understand the coding concepts/patterns you will discover through working hard, wikipedia is good help usually. You can also get good at basics by doing the first easiest challenges at projecteuler.net

You will probably do a lot of things wrong and end up with spaghetti code on your first projects but each time you 'reset' to a new project your quality should improve.

I also use JS a lot these days but you shouldn't think you will be JS dev you whole life, things are always changing quick, and depending on what you want to build, sometimes javascript is not a good tech choice.

Doing something like steemnow is definatly doable in less time than that, even for a junior dev. It's all client side connected to a steem node it's pretty elegant and KISS.