code improvements

packages/overlayscrollbars/src/autoUpdateLoop/autoUpdateLoop.ts

@@ -1,4 +1,4 @@
-import { rAF, cAF, isEmptyArray, indexOf, createCache, runEach } from 'support';
+import { rAF, cAF, isEmptyArray, indexOf, createCache, runEach, push } from 'support';
 import { getEnvironment } from 'environment';
 
 export interface AutoUpdateLoop {
@@ -40,7 +40,7 @@ const createAutoUpdateLoop = (): AutoUpdateLoop => {
   function interval(newInterval: number): () => void;
   function interval(newInterval?: number): number | (() => void) {
     if (newInterval) {
-      intervals.push(newInterval);
+      push(intervals, newInterval);
       updateLoopInterval();
 
       return () => {
@@ -53,7 +53,7 @@ const createAutoUpdateLoop = (): AutoUpdateLoop => {
 
   return {
     _add: (fn) => {
-      loopFunctions.push(fn);
+      push(loopFunctions, fn);
 
       if (!loopIsRunning && !isEmptyArray(loopFunctions)) {
         getEnvironment()._autoUpdateLoop = loopIsRunning = true;

packages/overlayscrollbars/src/observers/domObserver.ts

@@ -1,4 +1,4 @@
-import { each, indexOf, isString, MutationObserverConstructor, isEmptyArray, on, off, attr, is, find } from 'support';
+import { each, indexOf, isString, MutationObserverConstructor, isEmptyArray, on, off, attr, is, find, push } from 'support';
 
 type StringNullUndefined = string | null | undefined;
 
@@ -47,7 +47,7 @@ export const createDOMObserver = (
           const elements = eventName && selector && getElements(selector);
 
           if (elements) {
-            arr.push([eventName!, elements]);
+            push(arr, [eventName!, elements], true);
           }
         }
         return arr;
@@ -85,7 +85,7 @@ export const createDOMObserver = (
       targetStyleChanged = targetStyleChanged || (targetAttrChanged && styleChangingAttrChanged);
 
       if (targetAttrChanged) {
-        targetChangedAttrs.push(attributeName!);
+        push(targetChangedAttrs, attributeName!);
       }
       if (_observeContent) {
         const notOnlyAttrChanged = !isAttributesType;
@@ -93,9 +93,7 @@ export const createDOMObserver = (
         const contentFinalChanged =
           (notOnlyAttrChanged || contentAttrChanged) && (_ignoreContentChange ? !_ignoreContentChange(mutation, target, options) : _observeContent);
 
-        each(addedNodes, (node) => {
+        push(totalAddedNodes, addedNodes);
-          totalAddedNodes.push(node);
-        });
 
         contentChanged = contentChanged || contentFinalChanged;
         childListChanged = childListChanged || isChildListType;
@@ -103,7 +101,15 @@ export const createDOMObserver = (
     });
 
     if (childListChanged && !isEmptyArray(totalAddedNodes)) {
-      refreshEventContentChange((selector) => totalAddedNodes.filter((node) => is(node as Element, selector)));
+      refreshEventContentChange((selector) =>
+        totalAddedNodes.reduce<Node[]>((arr, node) => {
+          push(arr, find(selector, node));
+          if (is(node, selector)) {
+            push(arr, node);
+          }
+          return arr;
+        }, [])
+      );
     }
     if (!isEmptyArray(targetChangedAttrs) || targetStyleChanged || contentChanged) {
       callback(targetChangedAttrs, targetStyleChanged, contentChanged);
@@ -123,7 +129,7 @@ export const createDOMObserver = (
   isConnected = true;
 
   if (_observeContent) {
-    refreshEventContentChange((selector) => find(selector, target) as Node[]);
+    refreshEventContentChange((selector) => find(selector, target));
   }
 
   return {

packages/overlayscrollbars/src/observers/sizeObserver.ts

@@ -16,6 +16,7 @@ import {
   addClass,
   isString,
   equalWH,
+  push,
   cAF,
   rAF,
   ResizeObserverConstructor,
@@ -61,7 +62,7 @@ export const createSizeObserver = (
   if (ResizeObserverConstructor) {
     const resizeObserverInstance = new ResizeObserverConstructor(onSizeChangedCallbackProxy);
     resizeObserverInstance.observe(listenerElement);
-    offListeners.push(() => resizeObserverInstance.disconnect());
+    push(offListeners, () => resizeObserverInstance.disconnect());
   } else {
     const observerElementChildren = createDOM(
       `<div class="${classNameSizeObserverListenerItem}" dir="ltr"><div class="${classNameSizeObserverListenerItem}"><div class="${classNameSizeObserverListenerItemFinal}"></div></div><div class="${classNameSizeObserverListenerItem}"><div class="${classNameSizeObserverListenerItemFinal}" style="width: 200%; height: 200%"></div></div></div>`
@@ -111,8 +112,7 @@ export const createSizeObserver = (
       return false;
     };
 
-    offListeners.push(on(expandElement, scrollEventName, onScroll));
+    push(offListeners, [on(expandElement, scrollEventName, onScroll), on(shrinkElement, scrollEventName, onScroll)]);
-    offListeners.push(on(shrinkElement, scrollEventName, onScroll));
 
     // lets assume that the divs will never be that large and a constant value is enough
     style(expandElementChild, {
@@ -125,7 +125,8 @@ export const createSizeObserver = (
 
   if (direction) {
     const updateDirectionCache = createCache(() => getDirection(sizeObserver));
-    offListeners.push(
+    push(
+      offListeners,
       on(sizeObserver, scrollEventName, (event: Event) => {
         const directionCache = updateDirectionCache();
         const { _value, _changed } = directionCache;
@@ -148,7 +149,7 @@ export const createSizeObserver = (
   // appearCallback is always needed on scroll-observer strategy to reset it
   if (appearCallback) {
     addClass(sizeObserver, classNameSizeObserverAppear);
-    offListeners.push(on(sizeObserver, animationStartEventName, appearCallback));
+    push(offListeners, on(sizeObserver, animationStartEventName, appearCallback));
   }
 
   prependChildren(target, sizeObserver);

packages/overlayscrollbars/src/observers/trinsicObserver.ts

@@ -1,4 +1,15 @@
-import { WH, Cache, createDOM, offsetSize, runEach, prependChildren, removeElements, createCache, IntersectionObserverConstructor } from 'support';
+import {
+  WH,
+  Cache,
+  createDOM,
+  offsetSize,
+  runEach,
+  prependChildren,
+  removeElements,
+  createCache,
+  push,
+  IntersectionObserverConstructor,
+} from 'support';
 import { createSizeObserver } from 'observers/sizeObserver';
 import { classNameTrinsicObserver } from 'classnames';
 
@@ -35,9 +46,10 @@ export const createTrinsicObserver = (
       { root: target }
     );
     intersectionObserverInstance.observe(trinsicObserver);
-    offListeners.push(() => intersectionObserverInstance.disconnect());
+    push(offListeners, () => intersectionObserverInstance.disconnect());
   } else {
-    offListeners.push(
+    push(
+      offListeners,
       createSizeObserver(trinsicObserver, () => {
         const newSize = offsetSize(trinsicObserver);
         const heightIntrinsicCache = updateHeightIntrinsicCache(0, newSize);

packages/overlayscrollbars/src/overlayscrollbars/OverlayScrollbars.ts

@@ -1,6 +1,6 @@
 import { OSTarget, OSTargetObject, CSSDirection } from 'typings';
 import { createStructureLifecycle } from 'lifecycles/structureLifecycle';
-import { Cache, appendChildren, addClass, contents, is, isHTMLElement, createDiv, each } from 'support';
+import { Cache, appendChildren, addClass, contents, is, isHTMLElement, createDiv, each, push } from 'support';
 import { createSizeObserver } from 'observers/sizeObserver';
 import { createTrinsicObserver } from 'observers/trinsicObserver';
 import { Lifecycle } from 'lifecycles/lifecycleBase';
@@ -44,7 +44,7 @@ const OverlayScrollbars = (target: OSTarget, options?: any, extensions?: any): v
   const lifecycles: Lifecycle<any>[] = [];
   const { host } = osTarget;
 
-  lifecycles.push(createStructureLifecycle(osTarget));
+  push(lifecycles, createStructureLifecycle(osTarget));
 
   // eslint-disable-next-line
   const onSizeChanged = (directionCache?: Cache<CSSDirection>) => {

packages/overlayscrollbars/src/support/dom/events.ts

@@ -1,4 +1,4 @@
-import { each, runEach } from 'support/utils/array';
+import { each, push, runEach } from 'support/utils/array';
 
 let passiveEventsSupport: boolean;
 const supportPassiveEvents = (): boolean => {
@@ -69,7 +69,7 @@ export const on = (target: EventTarget, eventNames: string, listener: EventListe
         }
       : listener;
 
-    offListeners.push(off.bind(null, target, eventName, finalListener, capture));
+    push(offListeners, off.bind(null, target, eventName, finalListener, capture));
     target.addEventListener(eventName, finalListener, nativeOptions);
   });
 

packages/overlayscrollbars/src/support/dom/traversal.ts

@@ -1,6 +1,7 @@
-import { each, from } from 'support/utils/array';
+import { isElement } from 'support/utils/types';
+import { push, from } from 'support/utils/array';
 
-type InputElementType = Element | null | undefined;
+type InputElementType = Element | Node | null | undefined;
 type OutputElementType = Element | null;
 
 const elmPrototype = Element.prototype;
@@ -12,12 +13,9 @@ const elmPrototype = Element.prototype;
  */
 const find = (selector: string, elm?: InputElementType): Element[] => {
   const arr: Array<Element> = [];
+  const rootElm = elm ? (isElement(elm) ? elm : null) : document;
 
-  each((elm || document).querySelectorAll(selector), (e: Element) => {
+  return rootElm ? push(arr, rootElm.querySelectorAll(selector)) : arr;
-    arr.push(e);
-  });
-
-  return arr;
 };
 
 /**
@@ -25,7 +23,11 @@ const find = (selector: string, elm?: InputElementType): Element[] => {
  * @param selector The selector which has to be searched by.
  * @param elm The element from which the search shall be outgoing.
  */
-const findFirst = (selector: string, elm?: InputElementType): OutputElementType => (elm || document).querySelector(selector);
+const findFirst = (selector: string, elm?: InputElementType): OutputElementType => {
+  const rootElm = elm ? (isElement(elm) ? elm : null) : document;
+
+  return rootElm ? rootElm.querySelector(selector) : null;
+};
 
 /**
  * Determines whether the passed element is matching with the passed selector.
@@ -33,12 +35,12 @@ const findFirst = (selector: string, elm?: InputElementType): OutputElementType
  * @param selector The selector which has to be compared with the passed element. Additional selectors: ':visible' and ':hidden'.
  */
 const is = (elm: InputElementType, selector: string): boolean => {
-  if (elm) {
+  if (isElement(elm)) {
     /* istanbul ignore next */
     // eslint-disable-next-line
     // @ts-ignore
-    const fn = elmPrototype.matches || elmPrototype.msMatchesSelector;
+    const fn: (...args: any) => boolean = elmPrototype.matches || elmPrototype.msMatchesSelector;
-    return fn && fn.call(elm, selector);
+    return fn.call(elm, selector);
   }
   return false;
 };
@@ -51,17 +53,12 @@ const is = (elm: InputElementType, selector: string): boolean => {
 const children = (elm: InputElementType, selector?: string): ReadonlyArray<Element> => {
   const childs: Array<Element> = [];
 
-  each(elm && elm.children, (child: Element) => {
+  return isElement(elm)
-    if (selector) {
+    ? push(
-      if (is(child, selector)) {
+        childs,
-        childs.push(child);
+        from(elm.children).filter((child) => (selector ? is(child, selector) : child))
-      }
+      )
-    } else {
+    : childs;
-      childs.push(child);
-    }
-  });
-
-  return childs;
 };
 
 /**
@@ -77,7 +74,7 @@ const contents = (elm: InputElementType): ReadonlyArray<ChildNode> => (elm ? fro
 const parent = (elm: InputElementType): OutputElementType => (elm ? elm.parentElement : null);
 
 const closest = (elm: InputElementType, selector: string): OutputElementType => {
-  if (elm) {
+  if (isElement(elm)) {
     // eslint-disable-next-line
     // @ts-ignore
     if (elmPrototype.closest) {
@@ -85,7 +82,7 @@ const closest = (elm: InputElementType, selector: string): OutputElementType =>
     }
     do {
       if (is(elm, selector)) {
-        return elm;
+        return elm as Element;
       }
       elm = parent(elm);
     } while (elm !== null && elm.nodeType === 1);

packages/overlayscrollbars/src/support/options/validation.ts

@@ -1,5 +1,5 @@
-import { each, hasOwnProperty, keys } from 'support/utils';
+import { each, hasOwnProperty, keys, push, isEmptyObject } from 'support/utils';
-import { type, isArray, isUndefined, isEmptyObject, isPlainObject, isString } from 'support/utils/types';
+import { type, isArray, isUndefined, isPlainObject, isString } from 'support/utils/types';
 import { OptionsTemplate, OptionsTemplateTypes, OptionsTemplateType, Func, OptionsValidationResult, OptionsValidated } from 'support/options';
 import { PlainObject } from 'typings';
 
@@ -93,13 +93,13 @@ const validateRecursive = <T extends PlainObject>(
           isValid = !!enumStringSplit.find((possibility) => possibility === optionsValue);
 
           // build error message
-          errorEnumStrings.push(...enumStringSplit);
+          push(errorEnumStrings, enumStringSplit);
         } else {
           isValid = optionsTemplateTypes[optionsValueType] === currTemplateType;
         }
 
         // build error message
-        errorPossibleTypes.push(isEnumString ? optionsTemplateTypes.string : typeString!);
+        push(errorPossibleTypes, isEnumString ? optionsTemplateTypes.string : typeString!);
 
         // continue if invalid, break if valid
         return !isValid;

packages/overlayscrollbars/src/support/utils/array.ts

@@ -1,4 +1,4 @@
-import { isArrayLike } from 'support/utils/types';
+import { isArrayLike, isString } from 'support/utils/types';
 import { PlainObject } from 'typings';
 
 type RunEachItem = ((...args: any) => any | any[]) | null | undefined;
@@ -55,6 +55,16 @@ export function each<T>(
  */
 export const indexOf = <T = any>(arr: Array<T>, item: T, fromIndex?: number): number => arr.indexOf(item, fromIndex);
 
+/**
+ * Pushesh all given items into the given array and returns it.
+ * @param array The array the items shall be pushed into.
+ * @param items The items which shall be pushed into the array.
+ */
+export const push = <T>(array: Array<T>, items: T | ArrayLike<T>, arrayIsSingleItem?: boolean): Array<T> => {
+  !arrayIsSingleItem && !isString(items) && isArrayLike(items) ? Array.prototype.push.apply(array, items as Array<T>) : array.push(items as T);
+  return array;
+};
+
 /**
  * Creates a shallow-copied Array instance from an array-like or iterable object.
  * @param arr The object from which the array instance shall be created.
@@ -65,7 +75,7 @@ export const from = <T = any>(arr: ArrayLike<T>) => {
   }
   const result: Array<T> = [];
   each(arr, (elm) => {
-    result.push(elm);
+    push(result, elm);
   });
   return result;
 };

packages/overlayscrollbars/src/support/utils/object.ts

@@ -72,3 +72,14 @@ export function assignDeep<T, U, V, W, X, Y, Z>(
   // Return the modified object
   return target as any;
 }
+
+/**
+ * Returns true if the given object is empty, false otherwise.
+ * @param obj The Object.
+ */
+export function isEmptyObject(obj: any): boolean {
+  /* eslint-disable no-restricted-syntax, guard-for-in */
+  for (const name in obj) return false;
+  return true;
+  /* eslint-enable */
+}

packages/overlayscrollbars/src/support/utils/types.ts

@@ -1,4 +1,7 @@
 import { PlainObject } from 'typings';
+import { hasOwnProperty } from 'support/utils/object';
+
+const ElementNodeType = Node.ELEMENT_NODE;
 
 export const type: (obj: any) => string = (obj) => {
   if (obj === undefined) return `${obj}`;
@@ -47,7 +50,9 @@ export function isObject(obj: any): boolean {
  */
 export function isArrayLike<T extends PlainObject = any>(obj: any): obj is ArrayLike<T> {
   const length = !!obj && obj.length;
-  return isArray(obj) || (!isFunction(obj) && isNumber(length) && length > -1 && length % 1 == 0); // eslint-disable-line eqeqeq
+  const lengthCorrectFormat = isNumber(length) && length > -1 && length % 1 == 0; // eslint-disable-line eqeqeq
+
+  return isArray(obj) || (!isFunction(obj) && lengthCorrectFormat) ? (length > 0 && isObject(obj) ? length - 1 in obj : true) : false;
 }
 
 /**
@@ -58,12 +63,13 @@ export function isPlainObject<T = any>(obj: any): obj is PlainObject<T> {
   if (!obj || !isObject(obj) || type(obj) !== 'object') return false;
 
   let key;
-  const proto = 'prototype';
+  const cstr = 'constructor';
-  const { hasOwnProperty } = Object[proto];
+  const ctor = obj[cstr];
-  const hasOwnConstructor = hasOwnProperty.call(obj, 'constructor');
+  const ctorProto = ctor && ctor.prototype;
-  const hasIsPrototypeOf = obj.constructor && obj.constructor[proto] && hasOwnProperty.call(obj.constructor[proto], 'isPrototypeOf');
+  const hasOwnConstructor = hasOwnProperty(obj, cstr);
+  const hasIsPrototypeOf = ctorProto && hasOwnProperty(ctorProto, 'isPrototypeOf');
 
-  if (obj.constructor && !hasOwnConstructor && !hasIsPrototypeOf) {
+  if (ctor && !hasOwnConstructor && !hasIsPrototypeOf) {
     return false;
   }
 
@@ -73,7 +79,7 @@ export function isPlainObject<T = any>(obj: any): obj is PlainObject<T> {
   }
   /* eslint-enable */
 
-  return isUndefined(key) || hasOwnProperty.call(obj, key);
+  return isUndefined(key) || hasOwnProperty(obj, key);
 }
 
 /**
@@ -81,18 +87,15 @@ export function isPlainObject<T = any>(obj: any): obj is PlainObject<T> {
  * @param obj The object which shall be checked.
  */
 export function isHTMLElement(obj: any): obj is HTMLElement {
-  const instaceOfRightHandSide = window.HTMLElement;
+  const instanceofObj = window.HTMLElement;
-  const doInstanceOf = isObject(instaceOfRightHandSide) || isFunction(instaceOfRightHandSide);
+  return obj ? (instanceofObj ? obj instanceof instanceofObj : obj.nodeType === ElementNodeType) : false;
-  return !!(doInstanceOf ? obj instanceof instaceOfRightHandSide : obj && isObject(obj) && obj.nodeType === 1 && isString(obj.nodeName));
 }
 
 /**
- * Returns true if the given object is empty, false otherwise.
+ * Checks whether the given object is a Element.
- * @param obj The Object.
+ * @param obj The object which shall be checked.
  */
-export function isEmptyObject(obj: any): boolean {
+export function isElement(obj: any): obj is Element {
-  /* eslint-disable no-restricted-syntax, guard-for-in */
+  const instanceofObj = window.Element;
-  for (const name in obj) return false;
+  return obj ? (instanceofObj ? obj instanceof instanceofObj : obj.nodeType === ElementNodeType) : false;
-  return true;
-  /* eslint-enable */
 }

packages/overlayscrollbars/tests/jsdom/support/dom/style.test.ts

@@ -1,4 +1,5 @@
-import { isString, isPlainObject, isEmptyObject } from 'support/utils/types';
+import { isEmptyObject } from 'support/utils/object';
+import { isString, isPlainObject } from 'support/utils/types';
 import { style, hide, show, topRightBottomLeft } from 'support/dom/style';
 
 describe('dom style', () => {

packages/overlayscrollbars/tests/jsdom/support/dom/traversal.test.ts

@@ -1,4 +1,4 @@
-import { find, findFirst, is, children, contents, parent, createDiv, liesBetween } from 'support/dom';
+import { find, findFirst, is, children, contents, parent, createDiv, liesBetween, createDOM } from 'support/dom';
 
 const slotElm = document.body;
 const testHTML = '<div id="parent" class="div-class"><div id="child" class="div-class"></div></div><p>2</p><input type="text" value="3"></input>abc';
@@ -55,6 +55,10 @@ describe('dom traversal', () => {
 
       expect(nonExistent.length).toBe(0);
     });
+
+    test('text node', () => {
+      expect(find('div', createDOM('<div>textnodehere</div>')[0].firstChild)).toEqual([]);
+    });
   });
 
   describe('findFirst', () => {
@@ -96,6 +100,10 @@ describe('dom traversal', () => {
 
       expect(nonExistent).toBe(null);
     });
+
+    test('text node', () => {
+      expect(findFirst('div', createDOM('<div>textnodehere</div>')[0].firstChild)).toEqual(null);
+    });
   });
 
   describe('is', () => {
@@ -147,6 +155,10 @@ describe('dom traversal', () => {
       expect(is(null, '.div-class')).toBe(false);
       expect(is(null, '.other-class')).toBe(false);
     });
+
+    test('text node', () => {
+      expect(is(createDOM('<div>textnodehere</div>')[0].firstChild, '.hi')).toEqual(false);
+    });
   });
 
   describe('children', () => {
@@ -169,6 +181,10 @@ describe('dom traversal', () => {
       expect(childs.length).toBe(1);
       expect(childs[0]).toBe(findFirst('input'));
     });
+
+    test('text node', () => {
+      expect(children(createDOM('<div>textnodehere</div>')[0].firstChild, '.hi')).toEqual([]);
+    });
   });
 
   describe('contents', () => {
@@ -184,6 +200,10 @@ describe('dom traversal', () => {
 
       expect(childs.length).toEqual(0);
     });
+
+    test('text node', () => {
+      expect(contents(createDOM('<div>textnodehere</div>')[0].firstChild)).toEqual([]);
+    });
   });
 
   describe('parent', () => {
@@ -198,6 +218,10 @@ describe('dom traversal', () => {
 
       expect(p).toBeNull();
     });
+
+    test('text node', () => {
+      expect(parent(createDOM('<div>textnodehere</div>')[0].firstChild)?.nodeName).toEqual('DIV');
+    });
   });
 
   describe('liesBetween', () => {
@@ -286,5 +310,9 @@ describe('dom traversal', () => {
 
       Element.prototype.closest = original;
     });
+
+    test('text node', () => {
+      expect(liesBetween(createDOM('<div>textnodehere</div>')[0].firstChild, '.a', '.b')).toEqual(false);
+    });
   });
 });

packages/overlayscrollbars/tests/jsdom/support/utils/arrays.test.ts

@@ -1,6 +1,87 @@
-import { each, from, indexOf, runEach } from 'support/utils/array';
+import { push, each, from, indexOf, runEach } from 'support/utils/array';
 
 describe('array utilities', () => {
+  describe('push', () => {
+    describe('single value', () => {
+      test('string', () => {
+        const arr: string[] = [];
+        const item = 'hi there';
+
+        expect(push(arr, item)).toBe(arr);
+
+        expect(arr).toHaveLength(1);
+        expect(arr[0]).toBe(item);
+      });
+
+      test('array like', () => {
+        const arr: string[] = [];
+        const item = ['tuple', 'elem'];
+
+        expect(push(arr, item, true)).toBe(arr);
+
+        expect(arr).toHaveLength(1);
+        expect(arr[0]).toBe(item);
+      });
+
+      test('array like fake', () => {
+        const arr: any[] = [];
+        const item = { length: 2 };
+
+        expect(push(arr, item)).toBe(arr);
+
+        expect(arr).toHaveLength(1);
+        expect(arr[0]).toBe(item);
+      });
+    });
+
+    describe('multiple values', () => {
+      test('string', () => {
+        const arr: string[] = [];
+        const items = 'hi there'.split('');
+
+        expect(push(arr, items)).toBe(arr);
+
+        expect(arr).toHaveLength(items.length);
+        expect(arr).toEqual(items);
+      });
+
+      test('array', () => {
+        const arr: string[] = [];
+        const items = ['tuple', 'elem'];
+
+        expect(push(arr, items)).toBe(arr);
+
+        expect(arr).toHaveLength(2);
+        expect(arr[0]).toBe('tuple');
+        expect(arr[1]).toBe('elem');
+      });
+
+      test('array like', () => {
+        const arr: string[] = [];
+        const items = { 0: 'zero', 1: 'one', 2: 'two', length: 3 };
+
+        expect(push(arr, items)).toBe(arr);
+
+        expect(arr).toHaveLength(3);
+        expect(arr[0]).toBe('zero');
+        expect(arr[1]).toBe('one');
+        expect(arr[2]).toBe('two');
+      });
+
+      test('array like query selector', () => {
+        document.body.innerHTML = '<div><p>testtext<h1></h1></p><div></div></div>';
+        const arr: Node[] = [];
+        const items = document.querySelectorAll('*');
+
+        expect(push(arr, items)).toBe(arr);
+
+        expect(arr).not.toHaveLength(0);
+        arr.forEach((node) => {
+          expect(node instanceof window.Element).toBe(true);
+        });
+      });
+    });
+  });
   describe('each', () => {
     describe('each through Array', () => {
       test('returns input', () => {
@@ -170,6 +251,13 @@ describe('array utilities', () => {
         expect(testFunc).toBeCalledTimes(arrLikeObj.length - 1);
       });
     });
+
+    describe('each through nothing', () => {
+      test('returns input', () => {
+        expect(each(null, () => {})).toBe(null);
+        expect(each(undefined, () => {})).toBe(undefined);
+      });
+    });
   });
 
   describe('from', () => {

packages/overlayscrollbars/tests/jsdom/support/utils/object.test.ts

@@ -1,4 +1,4 @@
-import { assignDeep, keys, hasOwnProperty } from 'support/utils/object';
+import { assignDeep, keys, hasOwnProperty, isEmptyObject } from 'support/utils/object';
 import { isPlainObject } from 'support/utils/types';
 
 describe('object utilities', () => {
@@ -164,6 +164,20 @@ describe('object utilities', () => {
     });
   });
 
+  describe('isEmptyObject', () => {
+    test('empty object is empty', () => {
+      expect(isEmptyObject({})).toBe(true);
+    });
+
+    test('filled object is not empty', () => {
+      expect(isEmptyObject({ a: 1, b: 2 })).toBe(false);
+    });
+
+    test('created object is empty', () => {
+      expect(isEmptyObject(Object.create(null))).toBe(true);
+    });
+  });
+
   test('hasOwnProperty', () => {
     const obj = {
       a: 1,

packages/overlayscrollbars/tests/jsdom/support/utils/types.test.ts

@@ -1,3 +1,4 @@
+import { createDOM } from 'support/dom/create';
 import {
   type,
   isNumber,
@@ -10,7 +11,7 @@ import {
   isNull,
   isArrayLike,
   isPlainObject,
-  isEmptyObject,
+  isElement,
   isHTMLElement,
 } from 'support/utils/types';
 
@@ -46,6 +47,7 @@ const typeNameValueMap = {
   window,
   body: document.body,
   querySelectorAll: document.querySelectorAll('*'),
+  textNode: createDOM('<div>textnodehere</div>')[0].firstChild,
 };
 
 const testTypeFn = (typeFunc: Function, expectedTypeNameValueResultMap: any) => {
@@ -130,6 +132,7 @@ describe('types', () => {
       document: true,
       window: true,
       body: true,
+      textNode: true,
       querySelectorAll: true,
       functionConstructor: true,
       arrayLikeObject: true,
@@ -177,30 +180,29 @@ describe('types', () => {
     });
   });
 
-  test('isEmptyObject', () => {
+  test('isElement', () => {
-    testTypeFn(isEmptyObject, {
+    const temp = window.Element;
-      objectEmpty: true,
-      objectCreate: true,
-      arrayEmpty: true,
 
-      newNumber: true,
+    testTypeFn(isElement, {
-      newBoolean: true,
+      body: true,
-      newFunction: true,
-      newArray: true,
-
-      null: true,
-      undefined: true,
-      booleanTrue: true,
-      booleanFalse: true,
-      void0: true,
-      number: true,
-      infinity: true,
-      functionConstructor: true,
-      function: true,
-      functionAsync: true,
-      functionArrow: true,
-      functionArrowAsync: true,
     });
+    Array.from(document.querySelectorAll('*')).forEach((elm) => {
+      expect(isElement(elm)).toBeTruthy();
+    });
+
+    // @ts-ignore
+    delete window.Element;
+    // @ts-ignore
+    window.Element = null;
+
+    testTypeFn(isElement, {
+      body: true,
+    });
+    Array.from(document.querySelectorAll('*')).forEach((elm) => {
+      expect(isElement(elm)).toBeTruthy();
+    });
+
+    window.Element = temp;
   });
 
   test('isHTMLElement', () => {
@@ -213,6 +215,7 @@ describe('types', () => {
       expect(isHTMLElement(elm)).toBeTruthy();
     });
 
+    // @ts-ignore
     delete window.HTMLElement;
     // @ts-ignore
     window.HTMLElement = null;

packages/overlayscrollbars/tests/puppeteer/observers/domObserver/index.browser.ts

@@ -28,10 +28,12 @@ const contentHostElmAttrChange: HTMLElement | null = document.querySelector('#co
 const targetElmsSlot = document.querySelector('#target .host-nest-item');
 const targetContentElmsSlot = document.querySelector('#target .content .content-nest');
 const targetContentBetweenElmsSlot = document.querySelector('#content-host');
+const imgElmsSlot = document.querySelector('#target .content-nest');
 
 const addRemoveTargetElms: HTMLButtonElement | null = document.querySelector('#addRemoveTargetElms');
 const addRemoveTargetContentElms: HTMLButtonElement | null = document.querySelector('#addRemoveTargetContentElms');
 const addRemoveTargetContentBetweenElms: HTMLButtonElement | null = document.querySelector('#addRemoveTargetContentBetweenElms');
+const addImgElms: HTMLButtonElement | null = document.querySelector('#addImgElms');
 const setTargetAttr: HTMLSelectElement | null = document.querySelector('#setTargetAttr');
 const setFilteredTargetAttr: HTMLSelectElement | null = document.querySelector('#setFilteredTargetAttr');
 const setContentAttr: HTMLSelectElement | null = document.querySelector('#setContentAttr');
@@ -48,7 +50,7 @@ const startBtn: HTMLButtonElement | null = document.querySelector('#start');
 const targetElmObservations: DOMObserverResult[] = [];
 const targetElmContentElmObservations: DOMObserverResult[] = [];
 const getTotalObservations = () => targetElmObservations.length + targetElmContentElmObservations.length;
-const getLast = <T>(arr: T[]): T => arr[arr.length - 1] || ({} as T);
+const getLast = <T>(arr: T[], indexFromLast = 0): T => arr[arr.length - 1 - indexFromLast] || ({} as T);
 const changedThrough = (observationLists?: Array<DOMObserverResult[]> | DOMObserverResult[]) => {
   interface Stat {
     total: number;
@@ -229,6 +231,37 @@ const addRemoveTargetContentElmsFn = async () => {
 const addRemoveTargetContentBetweenElmsFn = async () => {
   await addRemoveElementsTest(targetContentBetweenElmsSlot, targetElmContentElmObservations);
 };
+const addImgElmsFn = async () => {
+  const add = async () => {
+    const img = new Image(1, 1);
+    img.src = 'data:image/gif;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=';
+    const { before, after, compare } = changedThrough(targetElmContentElmObservations);
+    const imgHolder = createDiv('img');
+    appendChildren(imgHolder, img);
+
+    before();
+    appendChildren(imgElmsSlot, imgHolder);
+
+    await waitForOrFailTest(() => {
+      after();
+      compare(2);
+
+      const mutationObserverObservation = getLast(targetElmContentElmObservations, 1);
+      should(mutationObserverObservation.contentChanged).equal(true);
+      should(mutationObserverObservation.styleChanged).equal(false);
+      should(mutationObserverObservation.changedTargetAttrs.length).equal(0);
+
+      const eventObservation = getLast(targetElmContentElmObservations);
+      should(eventObservation.contentChanged).equal(true);
+      should(eventObservation.styleChanged).equal(false);
+      should(eventObservation.changedTargetAttrs.length).equal(0);
+    });
+  };
+
+  await add();
+  await add();
+  await add();
+};
 const iterateTargetAttrChange = async () => {
   await iterateAttrChange(setTargetAttr, targetElmObservations, (observation, selected) => {
     const { changedTargetAttrs, styleChanged, contentChanged } = observation;
@@ -270,6 +303,7 @@ const triggerBetweenSummaryChange = async () => {
 addRemoveTargetElms?.addEventListener('click', addRemoveTargetElmsFn);
 addRemoveTargetContentElms?.addEventListener('click', addRemoveTargetContentElmsFn);
 addRemoveTargetContentBetweenElms?.addEventListener('click', addRemoveTargetContentBetweenElmsFn);
+addImgElms?.addEventListener('click', addImgElmsFn);
 setTargetAttr?.addEventListener('change', attrChangeListener(targetElm));
 setFilteredTargetAttr?.addEventListener('change', attrChangeListener(targetElm));
 setContentAttr?.addEventListener('change', attrChangeListener(contentElmAttrChange));
@@ -305,6 +339,9 @@ createDOMObserver(
   },
   {
     _observeContent: true,
+    _eventContentChange: () => {
+      return [['img', 'load']];
+    },
     _ignoreContentChange: (mutation) => {
       const { target, attributeName } = mutation;
       return attributeName ? !hasClass(target as Element, 'host') && liesBetween(target as Element, '.host', '.content') : false;
@@ -315,6 +352,8 @@ createDOMObserver(
 const start = async () => {
   setTestResult(null);
 
+  await addImgElmsFn();
+
   await addRemoveTargetElmsFn();
   await addRemoveTargetContentElmsFn();
   await addRemoveTargetContentBetweenElmsFn();

packages/overlayscrollbars/tests/puppeteer/observers/domObserver/index.html

@@ -2,6 +2,7 @@
   <button id="addRemoveTargetElms">Target Elements</button>
   <button id="addRemoveTargetContentElms">Content Elements</button>
   <button id="addRemoveTargetContentBetweenElms">Content Between Elements</button>
+  <button id="addImgElms">Image Elements</button>
 
   <label for="setTargetAttr">setTargetAttr</label>
   <select name="setTargetAttr" id="setTargetAttr">

packages/overlayscrollbars/tests/puppeteer/observers/domObserver/index.scss

@@ -75,3 +75,14 @@ body {
     }
   }
 }
+
+.img {
+  background: lime;
+  width: 50px;
+  height: 50px;
+
+  img {
+    opacity: 0;
+    visibility: hidden;
+  }
+}