Every tick save the state of all the mobs and add it to an array

[Wazzaps]

OK so what I am trying to do here is make a "recorder" which doesn't record video, but instead the entities, tile entities, block changes, etc. So my first goal is entities. I searched the events section for an onTick event, but I didn't find anything. Then, If I get access to an onTick event(or something else) with world access, how do I get the pos,rot,etc of all the entities? Then, How do I add all of these to an array (efficiently(I know basic Java but I came from JavaScript and there this task seems alot easier)) Thanks in advance. (PS. I am new to modding)