zjquery: Add closest() method.

frontend_tests/node_tests/zjquery.js

@@ -210,3 +210,31 @@ run_test('extensions', () => {
     // But we also have area available from general extension.
     assert.equal(rect.area(), 35);
 });
+
+run_test('closest', () => {
+    var widget = $('#my-widget');
+    var parent;
+    var parentSelector;
+
+    parentSelector = '#my-parent';
+    parent = $(parentSelector);
+    widget.set_parent(parent);
+    assert.equal(widget.closest('#my-parent').selector, parentSelector);
+
+    parentSelector = '<div id="my-parent"></div>';
+    parent = $(parentSelector);
+    widget.set_parent(parent);
+    assert.equal(widget.closest('#my-parent').selector, parentSelector);
+
+    parentSelector = '<div class="parent-class"></div>';
+    parent = $(parentSelector);
+    widget.set_parent(parent);
+    assert.equal(widget.closest('.parent-class').selector, parentSelector);
+
+    parentSelector = '#my-parent';
+    parent = $(parentSelector);
+    widget.set_parents_result(parentSelector, parent);
+    assert.equal(widget.closest('#my-parent').selector, parentSelector);
+
+    assert.equal(widget.closest('#bogus-parent').selector, undefined);
+});

frontend_tests/zjsunit/zjquery.js

@@ -163,6 +163,18 @@ exports.make_new_elem = function (selector, opts) {
             event_store.generic_event('click', arg);
             return self;
         },
+        closest: function (selector) {
+            var elem = self;
+            var search = selector.startsWith('.') || selector.startsWith('#') ? selector.substring(1) : selector;
+            if (elem.selector.indexOf(search) > -1) {
+                return elem;
+            } else if (parents_result.get(selector)) {
+                return parents_result.get(selector);
+            } else if (!elem.parent()) {
+                return [];
+            }
+            return elem.parent().closest(selector);
+        },
         data: noop,
         delay: function () {
             return self;