lodash/internal/assignOwnDefaults.js

define([], function() {

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

  /** Used for native method references. */
  var objectProto = Object.prototype;

  /** Used to check objects for own properties. */
  var hasOwnProperty = objectProto.hasOwnProperty;

  /**
   * Used by `_.template` to customize its `_.assign` use.
   *
   * **Note:** This function is like `assignDefaults` except that it ignores
   * inherited property values when checking if a property is `undefined`.
   *
   * @private
   * @param {*} objectValue The destination object property value.
   * @param {*} sourceValue The source object property value.
   * @param {string} key The key associated with the object and source values.
   * @param {Object} object The destination object.
   * @returns {*} Returns the value to assign to the destination object.
   */
  function assignOwnDefaults(objectValue, sourceValue, key, object) {
    return (objectValue === undefined || !hasOwnProperty.call(object, key))
      ? sourceValue
      : objectValue;
  }

  return assignOwnDefaults;
});