filter out undefined fields

index.js

@@ -93,15 +93,14 @@ function recursive_filter (input, filters, children_key = 'children') {
     data[i] = e;
     let match = true;
     for (const filter of filters) {
-      let search_str = '';
-      if (
-        typeof filter.fields !== 'undefined'
-        && Array.isArray (filter.fields)
-      ) {
-        search_str = filter.fields.map ((f) => e[f])
-          .join (' ');
-      }
-      else { search_str = e[filter.field]; }
+      const is_multi_filter
+      = Array.isArray (filter.fields);
+
+      const search_str = is_multi_filter
+        ? filter.fields.map ((f) => e[f])
+          .filter ((v) => typeof v !== 'undefined')
+          .join (' ')
+        : e[filter.field];
 
       if (!filter.filter.test (search_str)) {
         match = false;

test/index.js

@@ -188,3 +188,28 @@ test ('recursive filter multifield', (t) => {
   const result = util.recursive_filter (raw, [ filter ]);
   t.deepEqual (filtered, result);
 });
+
+test ('recursive filter multifield input error', (t) => {
+  t.notThrows (() => {
+    util.recursive_filter (
+      [ { foo: 'bar' } ],
+      [ { fields: '', field: 'foo', filter: /a/u } ]
+    );
+  });
+});
+
+test ('recursive filter undefined multifield', (t) => {
+  const res = util.recursive_filter (
+    [ { foo: 'bar' } ],
+    [
+      {
+        fields: [
+          'foo',
+          'bar'
+        ],
+        filter: /\s/u
+      }
+    ]
+  );
+  t.deepEqual (res, []);
+});