lodash/_copyObjectWith.js

define(['./_assignValue'], function(assignValue) {

  /**
   * This function is like `copyObject` except that it accepts a function to
   * customize copied values.
   *
   * @private
   * @param {Object} source The object to copy properties from.
   * @param {Array} props The property identifiers to copy.
   * @param {Object} [object={}] The object to copy properties to.
   * @param {Function} [customizer] The function to customize copied values.
   * @returns {Object} Returns `object`.
   */
  function copyObjectWith(source, props, object, customizer) {
    object || (object = {});

    var index = -1,
        length = props.length;

    while (++index < length) {
      var key = props[index];

      var newValue = customizer
        ? customizer(object[key], source[key], key, object, source)
        : source[key];

      assignValue(object, key, newValue);
    }
    return object;
  }

  return copyObjectWith;
});