array/fold.js

  1. /**
  2.  * @function fold
  3.  * @description Autocurried function which returns a single item by mapping over the provided array and calls an iterator function
  4.  * @param {cbFunction} cb - Callback function to modify the item
  5.  * @param {*} init - Initial value
  6.  * @param {Array} a - Array with items to modify by the cb function
  7.  * @returns {*}
  8.  * @see reduce
  9.  * @since 1.0.2
  10.  * @example
  11.  *
  12.  * const result = fold(add, 0, [1,1,1])
  13.  * // result = 3
  14.  */
  16. /**
  17.  * @callback cbFunction
  18.  * @param {*} r - Accumulator which accumulates the callback's return values
  19.  * @param {*} item - the current element being processed
  20.  * @param {number} index - the indey of the item being processed
  21.  * @param {Array} a - The initial array
  22.  * @return {*}
  23.  */
  24. import curry from '../curry'
  26. export default curry(function fold (cb, init, a) {
  27.   let i = -1
  28.   const l = a.length
  29.   let r = init
  30.   while (++i < l) {
  31.     r = cb(r, a[i], i, a)
  32.   }
  33.   return r
  34. })