Add mouseMoveThenOver, test

assets/js/autocomplete.ts

@@ -8,6 +8,7 @@ import { getTermContexts } from './match_query';
 import store from './utils/store';
 import { TermContext } from './query/lex.ts';
 import { $, $$, makeEl, removeEl } from './utils/dom.ts';
+import { mouseMoveThenOver } from './utils/events.ts';
 
 type TermSuggestion = {
   label: string;
@@ -125,38 +126,18 @@ function createItem(list: HTMLUListElement, suggestion: TermSuggestion) {
     className: 'autocomplete__item',
   });
 
-  let ignoreMouseOver = true;
-
   item.textContent = suggestion.label;
   item.dataset.value = suggestion.value;
 
-  function onItemMouseOver() {
-    // Prevent selection when mouse entered the element without actually moving.
-    if (ignoreMouseOver) {
-      return;
-    }
-
+  mouseMoveThenOver(item, () => {
     removeSelected();
     item.classList.add('autocomplete__item--selected');
-  }
-
-  item.addEventListener('mouseover', onItemMouseOver);
+  });
 
   item.addEventListener('mouseout', () => {
     removeSelected();
   });
 
-  item.addEventListener(
-    'mousemove',
-    () => {
-      ignoreMouseOver = false;
-      onItemMouseOver();
-    },
-    {
-      once: true,
-    },
-  );
-
   item.addEventListener('click', () => {
     if (!inputField || !item.dataset.value) return;
 

assets/js/utils/__tests__/events.spec.ts

@@ -1,4 +1,4 @@
-import { delegate, fire, leftClick, on, PhilomenaAvailableEventsMap } from '../events';
+import { delegate, fire, mouseMoveThenOver, leftClick, on, PhilomenaAvailableEventsMap } from '../events';
 import { getRandomArrayItem } from '../../../test/randomness';
 import { fireEvent } from '@testing-library/dom';
 
@@ -80,6 +80,55 @@ describe('Event utils', () => {
     });
   });
 
+  describe('mouseMoveThenOver', () => {
+    it('should NOT fire on first mouseover', () => {
+      const mockButton = document.createElement('button');
+      const mockHandler = vi.fn();
+
+      mouseMoveThenOver(mockButton, mockHandler);
+
+      fireEvent.mouseOver(mockButton);
+
+      expect(mockHandler).toHaveBeenCalledTimes(0);
+    });
+
+    it('should fire on the first mousemove', () => {
+      const mockButton = document.createElement('button');
+      const mockHandler = vi.fn();
+
+      mouseMoveThenOver(mockButton, mockHandler);
+
+      fireEvent.mouseMove(mockButton);
+
+      expect(mockHandler).toHaveBeenCalledTimes(1);
+    });
+
+    it('should fire on subsequent mouseover', () => {
+      const mockButton = document.createElement('button');
+      const mockHandler = vi.fn();
+
+      mouseMoveThenOver(mockButton, mockHandler);
+
+      fireEvent.mouseMove(mockButton);
+      fireEvent.mouseOver(mockButton);
+
+      expect(mockHandler).toHaveBeenCalledTimes(2);
+    });
+
+    it('should NOT fire on subsequent mousemove', () => {
+      const mockButton = document.createElement('button');
+      const mockHandler = vi.fn();
+
+      mouseMoveThenOver(mockButton, mockHandler);
+
+      fireEvent.mouseMove(mockButton);
+      fireEvent.mouseOver(mockButton);
+      fireEvent.mouseMove(mockButton);
+
+      expect(mockHandler).toHaveBeenCalledTimes(2);
+    });
+  });
+
   describe('delegate', () => {
     it('should call the native addEventListener method on the element', () => {
       const mockElement = document.createElement('div');

assets/js/utils/events.ts

@@ -43,6 +43,17 @@ export function leftClick<E extends MouseEvent, Target extends EventTarget>(func
   };
 }
 
+export function mouseMoveThenOver<El extends HTMLElement>(element: El, func: (e: MouseEvent) => void) {
+  element.addEventListener(
+    'mousemove',
+    (event: MouseEvent) => {
+      func(event);
+      element.addEventListener('mouseover', func);
+    },
+    { once: true },
+  );
+}
+
 export function delegate<K extends keyof PhilomenaAvailableEventsMap, Target extends Element>(
   node: PhilomenaEventElement,
   event: K,