From df72a21fa89a4885bb666f4a3bc0a9e757b870c2 Mon Sep 17 00:00:00 2001
From: GeoSot <geo.sotis@gmail.com>
Date: Wed, 19 May 2021 01:23:52 +0300
Subject: [PATCH] Add `getNextActiveElement` helper function to utils,
 replacing custom implementation through components (#33608)

---
 js/src/carousel.js               | 17 ++------------
 js/src/dropdown.js               | 22 +++++-------------
 js/src/util/index.js             | 29 ++++++++++++++++++++++++
 js/tests/unit/util/index.spec.js | 39 ++++++++++++++++++++++++++++++++
 4 files changed, 76 insertions(+), 31 deletions(-)

diff --git a/js/src/carousel.js b/js/src/carousel.js
index bb894e9c37..7d197ab1ee 100644
--- a/js/src/carousel.js
+++ b/js/src/carousel.js
@@ -10,6 +10,7 @@ import {
   getElementFromSelector,
   isRTL,
   isVisible,
+  getNextActiveElement,
   reflow,
   triggerTransitionEnd,
   typeCheckConfig
@@ -337,21 +338,7 @@ class Carousel extends BaseComponent {
 
   _getItemByOrder(order, activeElement) {
     const isNext = order === ORDER_NEXT
-    const isPrev = order === ORDER_PREV
-    const activeIndex = this._getItemIndex(activeElement)
-    const lastItemIndex = this._items.length - 1
-    const isGoingToWrap = (isPrev && activeIndex === 0) || (isNext && activeIndex === lastItemIndex)
-
-    if (isGoingToWrap && !this._config.wrap) {
-      return activeElement
-    }
-
-    const delta = isPrev ? -1 : 1
-    const itemIndex = (activeIndex + delta) % this._items.length
-
-    return itemIndex === -1 ?
-      this._items[this._items.length - 1] :
-      this._items[itemIndex]
+    return getNextActiveElement(this._items, activeElement, isNext, this._config.wrap)
   }
 
   _triggerSlideEvent(relatedTarget, eventDirectionName) {
diff --git a/js/src/dropdown.js b/js/src/dropdown.js
index 565edb8929..cab2d018bb 100644
--- a/js/src/dropdown.js
+++ b/js/src/dropdown.js
@@ -16,6 +16,7 @@ import {
   isVisible,
   isRTL,
   noop,
+  getNextActiveElement,
   typeCheckConfig
 } from './util/index'
 import Data from './dom/data'
@@ -354,28 +355,17 @@ class Dropdown extends BaseComponent {
   }
 
   _selectMenuItem(event) {
+    if (![ARROW_UP_KEY, ARROW_DOWN_KEY].includes(event.key)) {
+      return
+    }
+
     const items = SelectorEngine.find(SELECTOR_VISIBLE_ITEMS, this._menu).filter(isVisible)
 
     if (!items.length) {
       return
     }
 
-    let index = items.indexOf(event.target)
-
-    // Up
-    if (event.key === ARROW_UP_KEY && index > 0) {
-      index--
-    }
-
-    // Down
-    if (event.key === ARROW_DOWN_KEY && index < items.length - 1) {
-      index++
-    }
-
-    // index is -1 if the first keydown is an ArrowUp
-    index = index === -1 ? 0 : index
-
-    items[index].focus()
+    getNextActiveElement(items, event.target, event.key === ARROW_DOWN_KEY, false).focus()
   }
 
   // Static
diff --git a/js/src/util/index.js b/js/src/util/index.js
index 9441d0a44a..6b38a05e94 100644
--- a/js/src/util/index.js
+++ b/js/src/util/index.js
@@ -261,6 +261,34 @@ const execute = callback => {
   }
 }
 
+/**
+ * Return the previous/next element of a list.
+ *
+ * @param {array} list    The list of elements
+ * @param activeElement   The active element
+ * @param shouldGetNext   Choose to get next or previous element
+ * @param isCycleAllowed
+ * @return {Element|elem} The proper element
+ */
+const getNextActiveElement = (list, activeElement, shouldGetNext, isCycleAllowed) => {
+  let index = list.indexOf(activeElement)
+
+  // if the element does not exist in the list initialize it as the first element
+  if (index === -1) {
+    return list[0]
+  }
+
+  const listLength = list.length
+
+  index += shouldGetNext ? 1 : -1
+
+  if (isCycleAllowed) {
+    index = (index + listLength) % listLength
+  }
+
+  return list[Math.max(0, Math.min(index, listLength - 1))]
+}
+
 export {
   getElement,
   getUID,
@@ -275,6 +303,7 @@ export {
   isDisabled,
   findShadowRoot,
   noop,
+  getNextActiveElement,
   reflow,
   getjQuery,
   onDOMContentLoaded,
diff --git a/js/tests/unit/util/index.spec.js b/js/tests/unit/util/index.spec.js
index b4010e0e0e..ca6430bee5 100644
--- a/js/tests/unit/util/index.spec.js
+++ b/js/tests/unit/util/index.spec.js
@@ -611,4 +611,43 @@ describe('Util', () => {
       expect(spy).toHaveBeenCalled()
     })
   })
+
+  describe('getNextActiveElement', () => {
+    it('should return first element if active not exists or not given', () => {
+      const array = ['a', 'b', 'c', 'd']
+
+      expect(Util.getNextActiveElement(array, '', true, true)).toEqual('a')
+      expect(Util.getNextActiveElement(array, 'g', true, true)).toEqual('a')
+    })
+
+    it('should return next element or same if is last', () => {
+      const array = ['a', 'b', 'c', 'd']
+
+      expect(Util.getNextActiveElement(array, 'a', true, true)).toEqual('b')
+      expect(Util.getNextActiveElement(array, 'b', true, true)).toEqual('c')
+      expect(Util.getNextActiveElement(array, 'd', true, false)).toEqual('d')
+    })
+
+    it('should return next element or first, if is last and "isCycleAllowed = true"', () => {
+      const array = ['a', 'b', 'c', 'd']
+
+      expect(Util.getNextActiveElement(array, 'c', true, true)).toEqual('d')
+      expect(Util.getNextActiveElement(array, 'd', true, true)).toEqual('a')
+    })
+
+    it('should return previous element or same if is first', () => {
+      const array = ['a', 'b', 'c', 'd']
+
+      expect(Util.getNextActiveElement(array, 'b', false, true)).toEqual('a')
+      expect(Util.getNextActiveElement(array, 'd', false, true)).toEqual('c')
+      expect(Util.getNextActiveElement(array, 'a', false, false)).toEqual('a')
+    })
+
+    it('should return next element or first, if is last and "isCycleAllowed = true"', () => {
+      const array = ['a', 'b', 'c', 'd']
+
+      expect(Util.getNextActiveElement(array, 'd', false, true)).toEqual('c')
+      expect(Util.getNextActiveElement(array, 'a', false, true)).toEqual('d')
+    })
+  })
 })