lodash/array/unzipWith.js

define(['../internal/arrayMap', '../internal/arrayReduce', '../internal/bindCallback', './unzip'], function(arrayMap, arrayReduce, bindCallback, unzip) {

  /** Used as a safe reference for `undefined` in pre-ES5 environments. */
  var undefined;

  /**
   * This method is like `_.unzip` except that it accepts an iteratee to specify
   * how regrouped values should be combined. The `iteratee` is bound to `thisArg`
   * and invoked with four arguments: (accumulator, value, index, group).
   *
   * @static
   * @memberOf _
   * @category Array
   * @param {Array} array The array of grouped elements to process.
   * @param {Function} [iteratee] The function to combine regrouped values.
   * @param {*} [thisArg] The `this` binding of `iteratee`.
   * @returns {Array} Returns the new array of regrouped elements.
   * @example
   *
   * var zipped = _.zip([1, 2], [10, 20], [100, 200]);
   * // => [[1, 10, 100], [2, 20, 200]]
   *
   * _.unzipWith(zipped, _.add);
   * // => [3, 30, 300]
   */
  function unzipWith(array, iteratee, thisArg) {
    var length = array ? array.length : 0;
    if (!length) {
      return [];
    }
    var result = unzip(array);
    if (iteratee == null) {
      return result;
    }
    iteratee = bindCallback(iteratee, thisArg, 4);
    return arrayMap(result, function(group) {
      return arrayReduce(group, iteratee, undefined, true);
    });
  }

  return unzipWith;
});