diff --git a/filter.js b/filter.js
new file mode 100644
index 0000000..29851f4
--- /dev/null
+++ b/filter.js
@@ -0,0 +1,114 @@
+'use strict';
+
+function get_element_field (element, carried_data, field) {
+  if (typeof carried_data[field] !== 'undefined')
+    return carried_data[field];
+  return element[field];
+}
+
+function check_filter (filter, e, carried_data) {
+  if (typeof filter.function !== 'undefined')
+    return filter.function ({ ...e, ...carried_data });
+
+  const search_str = Array.isArray (filter.field)
+    ? filter.field.map ((f) => get_element_field (e, carried_data, f))
+      .filter ((v) => typeof v !== 'undefined')
+      .join (' ')
+    : get_element_field (e, carried_data, filter.field);
+
+  return filter.filter.test (search_str);
+}
+
+function check_filters (filters, e, carried_data, or = false) {
+  for (const filter of filters) {
+    let res = false;
+    if (Array.isArray (filter.or))
+      res = check_filters (filter.or, e, carried_data, true);
+    else
+      res = check_filter (filter, e, carried_data);
+
+    if (or && res)
+      return true;
+    if (!res && !or)
+      return false;
+  }
+  return !or;
+}
+
+/**
+ * @typedef Filter
+ * @type {object}
+ * @property {string|string[]} field - fields to apply filter on
+ * @property {RegExp} filter - filter
+ */
+
+/**
+ * @typedef FilterFunction
+ * @type {object}
+ * @property {function} function - function to test element for match
+ */
+
+/**
+ * @typedef FilterOrGroup
+ * @type {object}
+ * @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 {FilterType[]} filters filters
+ * @param {string[]} carry carry data to children to match
+ * @param {object} carried_data internal: carried data
+ * @returns {Array<object>} filtered data
+ */
+function recursive_filter (
+  input,
+  filters,
+  children_key = 'children',
+  carry = [],
+  carried_data = {}
+) {
+  const data = [ ...input ];
+  const filtered = [];
+
+  for (const c of carry) {
+    if (typeof carried_data[c] !== 'string')
+      carried_data[c] = '';
+  }
+
+  for (let i = 0; i < data.length; i++) {
+    const e = { ...data[i] };
+    data[i] = e;
+    const sub_carry = { ...carried_data };
+    for (const c of carry) {
+      if (typeof e[c] !== 'undefined')
+        sub_carry[c] += `${sub_carry[c].length > 0 ? ' ' : ''}${e[c]}`;
+    }
+    if (check_filters (filters, e, sub_carry)) {
+      filtered.push (e);
+    }
+    else {
+      if (typeof e[children_key] === 'undefined')
+        continue;
+      e[children_key] = recursive_filter (
+        e[children_key],
+        filters,
+        children_key,
+        carry,
+        sub_carry
+      );
+      if (e[children_key].length > 0)
+        filtered.push (e);
+    }
+  }
+  return filtered;
+}
+
+module.exports = recursive_filter;
diff --git a/index.js b/index.js
index 1958192..999e9cd 100644
--- a/index.js
+++ b/index.js
@@ -7,6 +7,8 @@
 
 'use strict';
 
+const recursive_filter = require ('./filter');
+
 /**
  * truncates a floating point number
  *
@@ -78,117 +80,6 @@ function is_nil (obj) {
       || (typeof obj === 'number' && isNaN (obj));
 }
 
-function get_element_field (element, carried_data, field) {
-  if (typeof carried_data[field] !== 'undefined')
-    return carried_data[field];
-  return element[field];
-}
-
-function check_filter (filter, e, carried_data) {
-  if (typeof filter.function !== 'undefined')
-    return filter.function ({ ...e, ...carried_data });
-
-  const search_str = Array.isArray (filter.field)
-    ? filter.field.map ((f) => get_element_field (e, carried_data, f))
-      .filter ((v) => typeof v !== 'undefined')
-      .join (' ')
-    : get_element_field (e, carried_data, filter.field);
-
-  return filter.filter.test (search_str);
-}
-
-function check_filters (filters, e, carried_data, or = false) {
-  for (const filter of filters) {
-    let res = false;
-    if (Array.isArray (filter.or))
-      res = check_filters (filter.or, e, carried_data, true);
-    else
-      res = check_filter (filter, e, carried_data);
-
-    if (or && res)
-      return true;
-    if (!res && !or)
-      return false;
-  }
-  return !or;
-}
-
-/**
- * @typedef Filter
- * @type {object}
- * @property {string|string[]} field - fields to apply filter on
- * @property {RegExp} filter - filter
- */
-
-/**
- * @typedef FilterFunction
- * @type {object}
- * @property {function} function - function to test element for match
- */
-
-/**
- * @typedef FilterOrGroup
- * @type {object}
- * @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 {FilterType[]} filters filters
- * @param {string[]} carry carry data to children to match
- * @param {object} carried_data internal: carried data
- * @returns {Array<object>} filtered data
- */
-function recursive_filter (
-  input,
-  filters,
-  children_key = 'children',
-  carry = [],
-  carried_data = {}
-) {
-  const data = [ ...input ];
-  const filtered = [];
-
-  for (const c of carry) {
-    if (typeof carried_data[c] !== 'string')
-      carried_data[c] = '';
-  }
-
-  for (let i = 0; i < data.length; i++) {
-    const e = { ...data[i] };
-    data[i] = e;
-    const sub_carry = { ...carried_data };
-    for (const c of carry) {
-      if (typeof e[c] !== 'undefined')
-        sub_carry[c] += `${sub_carry[c].length > 0 ? ' ' : ''}${e[c]}`;
-    }
-    if (check_filters (filters, e, sub_carry)) {
-      filtered.push (e);
-    }
-    else {
-      if (typeof e[children_key] === 'undefined')
-        continue;
-      e[children_key] = recursive_filter (
-        e[children_key],
-        filters,
-        children_key,
-        carry,
-        sub_carry
-      );
-      if (e[children_key].length > 0)
-        filtered.push (e);
-    }
-  }
-  return filtered;
-}
-
 module.exports = {
   truncate_decimal,
   try_parse_json,
diff --git a/package.json b/package.json
index d150843..eae26a2 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@sapphirecode/utilities",
-  "version": "1.8.7",
+  "version": "1.8.8",
   "main": "index.js",
   "author": {
     "name": "Timo Hocker",
@@ -36,8 +36,8 @@
   },
   "files": [
     "LICENSE",
-    "index.js",
-    "index.d.ts"
+    "*.js",
+    "*.d.ts"
   ],
   "engines": {
     "node": ">=10"