Don't waste your time with Facebook unless you're desperate. Like the other people mentioned here, there is something fishy going on with Facebook interviews.

I really did well with the onsite interview, and they told me that they passed on my application with no feedback after two weeks.

I've gone through two phone interviews and then an onsite interview with three coding (ninja), one design (pirate), and one cultural/coding (jedi) interview.

I have heard that they usually do only two ninja interviews, but I got three for some reason.

The coding interviews are pretty standard. You either got it right or not.

Explain everything clearly as you code it, because they may not understand your solution even if it's an optimal solution. Be prepared for follow-up questions after that.

Since I got the coding questions right, I was asked a second one each time.

So, on a successful interview, be prepared to do seven coding questions (again, five in most cases).

I cannot go into specifics because of the NDA, but they are standard coding questions. You can find similar questions on LeetCode or in coding interview prep books.