diff --git a/index.js b/index.js
index 662ee59..1958192 100644
--- a/index.js
+++ b/index.js
@@ -120,17 +120,28 @@ function check_filters (filters, e, carried_data, or = false) {
  * @property {RegExp} filter - filter
  */
 
+/**
+ * @typedef FilterFunction
+ * @type {object}
+ * @property {function} function - function to test element for match
+ */
+
 /**
  * @typedef FilterOrGroup
  * @type {object}
- * @property {(Filter|FilterOrGroup)[]} or - create an OR group of filters
+ * @property {FilterType[]} or - create an OR group of filters
+ */
+
+/**
+ * @typedef FilterType
+ * @type {Filter|FilterFunction|FilterOrGroup}
  */
 
 /**
  * filter nested objects
  *
  * @param {Array<object>} input object to filter
- * @param {(Filter|FilterOrGroup)[]} filters filters
+ * @param {FilterType[]} filters filters
  * @param {string[]} carry carry data to children to match
  * @param {object} carried_data internal: carried data
  * @returns {Array<object>} filtered data