* core: add dom helper to listen resize of elements.

lib/core/src/dom/index.ts

@@ -3,3 +3,4 @@ export * from './run-js';
 export * from './scroll-into-view';
 export * from './get-lib';
 export * from './is-detached';
+export * from './resize';

lib/core/src/dom/resize.ts

@@ -0,0 +1,30 @@
+import {$, Cash, Selector} from '../cash';
+
+/**
+ * Listen element resize with ResizeObserver.
+ *
+ * @param selector Element selector to check.
+ * @returns True if the element is disabled.
+ */
+export function listenResize(selector: Selector, callback: ResizeObserverCallback): ResizeObserver {
+    const $elements = $(selector);
+    const observer = new ResizeObserver(callback);
+
+    $elements.each((_, ele) => {
+        observer.observe(ele);
+    });
+
+    return observer;
+}
+
+/* Declare types. */
+declare module 'cash-dom' {
+    interface Cash {
+        resize(callback: ResizeObserverCallback): ResizeObserver;
+    }
+}
+
+/* Extend as $.fn.resize() */
+$.fn.resize = function (this: Cash, callback: ResizeObserverCallback) {
+    return listenResize(this, callback);
+};