Add test for using function to select element

Move dockblock

Fix import path for closest

Resolving merge conflict error

Fix linting errors

src/shared/utils/closest/closest.js

@@ -3,6 +3,15 @@ const matchFunction = Element.prototype.matches ||
                       Element.prototype.mozMatchesSelector ||
                       Element.prototype.msMatchesSelector;
 
+/**
+ * Get the closest parent element of a given element that matches the given
+ * selector string or matching function
+ *
+ * @param {Element} element The child element to find a parent of
+ * @param {String|Function} selector The string or function to use to match
+ *     the parent element
+ * @return {Element|null}
+ */
 export default function closest(element, value) {
   if (!element) {
     return null;

src/shared/utils/closest/tests/closest.test.js

@@ -1,9 +1,9 @@
-import {closest} from 'utils';
-
 import {
   createSandbox,
 } from 'helper';
 
+import closest from './../closest';
+
 const sampleMarkup = `
   <div class="tree">
     <section class="branch">
@@ -48,6 +48,18 @@ describe('utils', () => {
     expect(closest(element, '.leaf')).toBe(null);
   });
 
+  test('should match element via callback', () => {
+    const element = sandbox.querySelector('.leaf');
+
+    function callback(currentElement) {
+      return currentElement
+        .classList
+        .contains('leaf');
+    }
+
+    expect(closest(element, callback)).toBe(element);
+  });
+
   [
     '.twig',
     'ul',