online binding

packages/svelte/src/reactivity/window/index.js

@@ -96,6 +96,21 @@ export const screenTop = new ReactiveValue(
 	}
 );
 
+/**
+ * `online.current` is a reactive view of `navigator.onLine`. On the server it is `undefined`
+ */
+export const online = new ReactiveValue(
+	BROWSER ? () => navigator.onLine : () => undefined,
+	(update) => {
+		const unsub_online = on(window, 'online', update);
+		const unsub_offline = on(window, 'offline', update);
+		return () => {
+			unsub_online();
+			unsub_offline();
+		};
+	}
+);
+
 /**
  * `devicePixelRatio.current` is a reactive view of `window.devicePixelRatio`. On the server it is `undefined`.
  * Note that behaviour differs between browsers — on Chrome it will respond to the current zoom level,

packages/svelte/types/index.d.ts

@@ -1995,6 +1995,10 @@ declare module 'svelte/reactivity/window' {
 	 * `screenTop.current` is a reactive view of `window.screenTop`. On the server it is `undefined`
 	 */
 	export const screenTop: ReactiveValue<number | undefined>;
+	/**
+	 * `online.current` is a reactive view of `navigator.onLine`. On the server it is `undefined`
+	 */
+	export const online: ReactiveValue<boolean | undefined>;
 	/**
 	 * `devicePixelRatio.current` is a reactive view of `window.devicePixelRatio`. On the server it is `undefined`.
 	 * Note that behaviour differs between browsers — on Chrome it will respond to the current zoom level,