Avoiding bad companies starts at the job interview. Remember that the job interview is not only for them to evaluate you, but also the other way around. Make sure to ask a lot of questions. What are they doing, how are they working, what help is there if you get stuck, are they doing code reviews, what will you be doing etc.

The job interview is the opportunity for you to get an inside view of the company. Don’t just accept any job because you are desperate. Luckily qualifies devs are much needed in companies.

Also, make sure to go to multiple job interviews so you can see the differences. I think it can be difficult to avoid in the beginning, but as you get more experience, you can sort of tell whether it’s a good or bad company at the job interview.

Though sometimes you are just unlucky. In that situation: leave. It is so good damn easy to get a job in this field.