1  var assignValue = require('./_assignValue'),
 2      baseAssignValue = require('./_baseAssignValue');
 3  
 4  /**
 5   * Copies properties of `source` to `object`.
 6   *
 7   * @private
 8   * @param {Object} source The object to copy properties from.
 9   * @param {Array} props The property identifiers to copy.
10   * @param {Object} [object={}] The object to copy properties to.
11   * @param {Function} [customizer] The function to customize copied values.
12   * @returns {Object} Returns `object`.
13   */
14  function copyObject(source, props, object, customizer) {
15    var isNew = !object;
16    object || (object = {});
17  
18    var index = -1,
19        length = props.length;
20  
21    while (++index < length) {
22      var key = props[index];
23  
24      var newValue = customizer
25        ? customizer(object[key], source[key], key, object, source)
26        : undefined;
27  
28      if (newValue === undefined) {
29        newValue = source[key];
30      }
31      if (isNew) {
32        baseAssignValue(object, key, newValue);
33      } else {
34        assignValue(object, key, newValue);
35      }
36    }
37    return object;
38  }
39  
40  module.exports = copyObject;