Split an array based on predicate function.

split-array.ts

/**
 * Splits array when splitOn function returns true. Matched item will kept and be first in the subsequent child array.
 * @param items
 * @param splitOn
 */
export const splitArray = <T>(
  items: T[],
  splitOn: (item: T) => boolean,
  keepSplitItem = true
): T[][] => {
  if (!items.length) return [];

  // split array by separators
  let master: T[][] = [];
  let split: T[] = [];
  items.forEach((item) => {
    if (splitOn(item)) {
      if (split.length) {
        master.push(split);
      }

      // add matched item to start of new sub split array
      if (keepSplitItem) {
        split = [{ ...item }];
      } else {
        split = [];
      }
    } else {
      split.push({ ...item });
    }
  });

  // catch any remaining items
  if (split.length) {
    master.push(split);
  }

  return master;
};