Added Firefox support for making Order Summary sticky when not longer than view (#49744)

* Added getComputedStyle for Firefox support

* Added changelog

* Reverted pnpm-lock.yaml

plugins/woocommerce-blocks/assets/js/base/hooks/use-observed-viewport.ts

@@ -43,10 +43,22 @@ export function useObservedViewport< T extends HTMLElement >(): [
 		const resizeObserver = new ResizeObserver( ( entries ) => {
 			entries.forEach( ( entry ) => {
 				if ( entry.target === element ) {
+					let elementTop = '0';
+
+					if ( element.computedStyleMap ) {
+						elementTop =
+							element
+								.computedStyleMap()
+								.get( 'top' )
+								?.toString() || elementTop;
+					} else {
+						// Firefox support
+						elementTop =
+							getComputedStyle( element ).top || elementTop;
+					}
+
 					const { height, width } = entry.contentRect;
-					const elementTop =
-						element.computedStyleMap().get( 'top' )?.toString() ||
-						'0';
+
 					setObservedElement( {
 						height: height + parseInt( elementTop, 10 ),
 						width,

plugins/woocommerce/changelog/49525-checkout-page-uncaught-typeerror-ecomputedstylemap-is-not-a-function

@@ -0,0 +1,5 @@
+Significance: patch
+Type: fix
+Comment: Added computedStyleMap for Firefox support in making the Order Summary sticky when not longer than view
+
+