over engineered reduce

Try to interpret this code:

 const [,startOfPP,,log] = jobList.reduce( ([acu, pp, prev, ppPrev], cur) => [ [...acu, cur] , cur.type === EVENT_TYPE.postProcess && prev.type !== EVENT_TYPE.postProcess ? cur : pp , cur , [...ppPrev, [pp, prev, cur]] ] , [[], null , {}, []]); 

At this moment I sad STOP! That is carzy! The base idea was I wrote a single pure reducer, which is give back startOfPP value and log. So I started 4 variable in local state: [[],

null , {}, []]

, but after take look back to code, I found this over engineered reducer solution.