ResizeObserver (utils/dom)
@ckeditor/ckeditor5-utils/src/dom/resizeobserver
A helper class which instances allow performing custom actions when native DOM elements are resized.
const editableElement = editor.editing.view.getDomRoot();
const observer = new ResizeObserver( editableElement, entry => {
console.log( 'The editable element has been resized in DOM.' );
console.log( entry.target ); // -> editableElement
console.log( entry.contentRect.width ); // -> e.g. '423px'
} );
By default, it uses the native DOM resize observer under the hood and in browsers that do not support the native API yet, a polyfilled observer is used instead.
Filtering
Properties
-
The callback executed each time
_elementis resized. -
The element observer by this observer.
Static properties
-
protected readonly static
_observerInstancemodule:utils/dom/resizeobserver~ResizeObserver._observerInstanceThe single native observer instance (or polyfill in browsers that do not support the API) shared across all
ResizeObserverinstances. -
private readonly static
_elementCallbacksmodule:utils/dom/resizeobserver~ResizeObserver._elementCallbacksA mapping of native DOM elements and their callbacks shared across all
ResizeObserverinstances.
Methods
-
constructor( element, callback )module:utils/dom/resizeobserver~ResizeObserver#constructorCreates an instance of the
ResizeObserverclass.Parameters
element : HTMLElementA DOM element that is to be observed for resizing. Note that the element must be visible (i.e. not detached from DOM) for the observer to work.
callback : functionA function called when the observed element was resized. It passes the
ResizeObserverEntryobject with information about the resize event.
-
destroy()module:utils/dom/resizeobserver~ResizeObserver#destroyDestroys the observer which disables the
callbackpassed to theconstructor.
Static methods
-
private static
_addElementCallback( element, callback )module:utils/dom/resizeobserver~ResizeObserver._addElementCallbackRegisters a new resize callback for the DOM element.
Parameters
element : HTMLElementcallback : function
-
Creates the single native observer shared across all
ResizeObserverinstances. If the browser does not support the native API, it creates a polyfill. -
private static
_deleteElementCallback( element, callback )module:utils/dom/resizeobserver~ResizeObserver._deleteElementCallbackRemoves a resize callback from the DOM element. If no callbacks are left for the element, it removes the element from the native observer.
Parameters
element : HTMLElementcallback : function
-
private static
_getElementCallbacks( element ) → Set.<HTMLElement> | nullmodule:utils/dom/resizeobserver~ResizeObserver._getElementCallbacksReturns are registered resize callbacks for the DOM element.
Parameters
element : HTMLElement
Returns
Set.<HTMLElement> | null
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