There are a multitude of resources online for learning to code, and it can be overwhelming to try and sift through resources looking for relevant and helpful learning materials. Below are some recommendations for resources which I used to prepare. I hope they are helpful in your studies!
Javascript Beginner’s Curriculum
This is a very comprehensive curriculum designed for specifically for Hack Reactor. But if you study everything here, you’ll be more than prepared for any other bootcamp as well.
Code School costs money, but it is ABSOLUTELY worth it.
Eloquent Javascript - I didn’t find the explanations that great, but the exercises are interesting and worth doing. I think Ch. 5 Higher Order functions is the best and most important chapter.
Coderbyte - You’ll need to learn RegExp to get through a lot of the problems. When I started out, some of the problems took me 45 minutes to complete. Don’t get discouraged. You’ll get better and faster through practice. If you spend an hour on a problem and still don’t get it, I would recommend just looking at the solution. I skipped the Medium challenges because they were very similar to the Easy challenges.
Frontend Masters - In addition to the Hack Reactor Workshop, I also did the Good Parts of Javascript Workshop taught by Douglas Crockford. He goes into a lot of detail about the language. I skipped most of it (due to lack of time) and focused on Fun with Functions Challenges. Doing those challenges will give you a strong understanding of callbacks and closure.
Lots of interesting coding challenges that are categorized by difficulty. Fullstack and Grace Hopper give T-shirts to students who reach 4 kyu by the end of the program, so you might as well get a head start in case you go to one of those schools.
String Methods and Array Methods
I used Anki flashcards to memorize all the string methods and array methods listed at W3Schools. You should know what parameters the methods take and what they return.
The instructor of this course wrote the Annotated Version of Eloquent Javascript. He ended up making his own course. You get to make a basic to-do list app in Javascript, and the course gives a taste of what programming  at work is like.
I also took two comp sci courses. They aren’t necessary for applying to bootcamps, but these courses covered a lot of topics that I’m now encountering at Grace Hopper. If you have the extra time, these are great for learning CS fundamentals, and the professors are great!
Takes about 3-6 months to complete depending on how much free time you have. This was one of my first introductions to coding. It was super challenging, but I loved it!
Compared to CS50, this course may seem a little dry compared to all the bells and whistles of CS50. However, I think the professor was really good at explaining concepts.
After going through all the materials above, I was more than prepared for my bootcamp technical interviews. Good luck with your preparation!