lodash/internal/mergeDefaults.js

import merge from '../object/merge';

/**
 * Used by `_.defaultsDeep` to customize its `_.merge` use.
 *
 * @private
 * @param {*} objectValue The destination object property value.
 * @param {*} sourceValue The source object property value.
 * @returns {*} Returns the value to assign to the destination object.
 */
function mergeDefaults(objectValue, sourceValue) {
  return objectValue === undefined ? sourceValue : merge(objectValue, sourceValue, mergeDefaults);
}

export default mergeDefaults;