allow custom functions in filters

test/index.js

@@ -252,3 +252,30 @@ test ('recursive filter carry field', (t) => {
     }
   ]);
 });
+
+test ('recursive filter custom function', (t) => {
+  const to_filter = [
+    {
+      name:     'foo',
+      children: [
+        { name: 'bar' },
+        { name: 'baz' },
+        { foo: 'bar' }
+      ]
+    }
+  ];
+
+  const res = util.recursive_filter (
+    to_filter,
+    [ { function: (elem) => elem.name === 'foo bar' } ],
+    'children',
+    [ 'name' ]
+  );
+
+  t.deepEqual (res, [
+    {
+      name:     'foo',
+      children: [ { name: 'bar' } ]
+    }
+  ]);
+});