Add useNavigatorOnLine hook

snippets/useNavigatorOnLine.md

@@ -0,0 +1,47 @@
+---
+title: useNavigatorOnLine
+tags: hooks,state,effect,intermediate
+---
+
+A hook that returns if the client is online or offline.
+
+- Create a function, `getOnLineStatus`, that uses the `NavigatorOnLine` web API to get the online status of the client.
+- Use the `React.useState()` hook to create an appropriate state variable, `status`, and setter.
+- Use the `React.useEffect()` hook to add listeners for appropriate events, updating state, and cleanup those listeners when unmounting.
+- Finally return the `status` state variable.
+
+```jsx
+const getOnLineStatus = () =>
+  typeof navigator !== "undefined" && typeof navigator.onLine === "boolean"
+    ? navigator.onLine
+    : true;
+
+const useNavigatorOnLine = () => {
+  const [status, setStatus] = React.useState(getOnLineStatus());
+
+  const setOnline = () => setStatus(true);
+  const setOffline = () => setStatus(false);
+
+  React.useEffect(() => {
+    window.addEventListener("online", setOnline);
+    window.addEventListener("offline", setOffline);
+
+    return () => {
+      window.removeEventListener("online", setOnline);
+      window.removeEventListener("offline", setOffline);
+    };
+  }, []);
+
+  return status;
+};
+```
+
+```jsx
+const StatusIndicator = () => {
+  const isOnline = useNavigatorOnLine();
+
+  return <span>You are {isOnline ? "online" : "offline"}.</span>;
+};
+
+ReactDOM.render(<StatusIndicator />, document.getElementById("root"));
+```