code: function copyObject(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)
          : undefined;
  
        assignValue(object, key, newValue === undefined ? source[key] : newValue);
      }
      return object;
    }
docs: Copies properties of `source` to `object`.
  
  @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`.