Ungrouped element batching w/ predicate

gistfile1.txt

export const batchMessages = <T,>(
  messages: T[],
  shouldBeBatched: (
    prevItem: T,
    nextItem: T,
  ) => boolean,
): T[][] =>
  messages?.reduce((acc: T[][], curr) => {
    const processed = acc.length
    const prevSubArr = acc[processed - 1]
    const lastElInPrevSubArr = prevSubArr?.[prevSubArr?.length - 1]

    if (prevSubArr != null && shouldBeBatched(lastElInPrevSubArr, curr)) {
      prevSubArr.push(curr)
    } else {
      acc.push([curr])
    }
    return acc
  }, [])