lodash/array/zipWith.js

define(['../function/restParam', './unzipWith'], function(restParam, unzipWith) {

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

  /**
   * This method is like `_.zip` except that it accepts an iteratee to specify
   * how grouped 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} [arrays] The arrays to process.
   * @param {Function} [iteratee] The function to combine grouped values.
   * @param {*} [thisArg] The `this` binding of `iteratee`.
   * @returns {Array} Returns the new array of grouped elements.
   * @example
   *
   * _.zipWith([1, 2], [10, 20], [100, 200], _.add);
   * // => [111, 222]
   */
  var zipWith = restParam(function(arrays) {
    var length = arrays.length,
        iteratee = length > 2 ? arrays[length - 2] : undefined,
        thisArg = length > 1 ? arrays[length - 1] : undefined;

    if (length > 2 && typeof iteratee == 'function') {
      length -= 2;
    } else {
      iteratee = (length > 1 && typeof thisArg == 'function') ? (--length, thisArg) : undefined;
      thisArg = undefined;
    }
    arrays.length = length;
    return unzipWith(arrays, iteratee, thisArg);
  });

  return zipWith;
});