While my question is similar to this question, my situation is a bit different.
I am part of a small development team consisting of two developers, my firend/colleague and myself. There is also a senior developer, but he is mainly focused on the database side, and does not write any code for the application itself.
I was intending to find another job (for various reasons, like the fact that the current job has a fairly long commute time and I also wanted to try my hand at something different). However, my friend/colleague announces that he got offered a job somewhere else and submitted his resignation. This blindsided me, since I had no idea he was also looking for another job. However this leaves me as the only developer who knows the details of how this application is structured (my friend/colleague had free rein to structure that part of the application as he pleased, but I still understand how the majority of it is structured).
Now unlike the question I linked to, I have no interest in figuring out what leverage I have over the company, I just want to know how to handle quitting without burning any bridges, since odds are I might leave before they can hire more developers for the project (they were already looking to hire developers before my friend/colleague quit). They are really great guys, but like I said, I am just looking for something else at this point so I would like to be as respectful of the situation as possible.