reduce

export default function reduce<T>(
  array: T[],
  callback: (
    previousValue: T,
    currentValue: T,
    currentIndex: number,
    array: T[]
  ) => T,
  initialValue?: T
) {
  const { length } = array
  if (length === 0 && isUndefined(initialValue)) {
    throw new Error('Reduce of empty array with no initial value')
  }

  let pre = initialValue ?? array[0]
  let i = isUndefined(initialValue) ? 1 : 0

  for (i; i < length; i++) {
    pre = callback(pre, array[i], i, array)
  }

  return pre
}

const isUndefined = (v: unknown) => typeof v === 'undefined'
#reduce

reduce
