Function reduce

reduce<T, U>(iterable, f, initial): U
The equivalent of Array.prototype.reduce for iterators.
Type Parameters
- T
- U
Parameters
- iterable: Iterable<T, any, any>
  The iterator to reduce.
- f: ((previous: U, current: T, index?: number) => U)
  The reducer function.
  - - (previous, current, index?): U
    - Parameters
      previous: U
      current: T
      Optionalindex: number
      Returns U
- initial: U
  The initial value to use for reduction.
Returns U