How to Check Internet Connection Status in Javascript

It returns a Boolean value that indicates whether the browser is connected to the internet (true) or not (false).

For example:

if (navigator.onLine) {
    console.log("You are online!");
} else {
    console.log("You are offline!");
}

You can also listen for changes in the internet connection status by using the online and offline events.

// Listen for when the browser goes online
window.addEventListener('online', function() {
    console.log("You are back online!");
});

// Listen for when the browser goes offline
window.addEventListener('offline', function() {
    console.log("You are offline!");
});

The navigator.onLine property only indicates if the browser is connected to a network, but it doesn't confirm if there's actual internet access. A device might be connected to a local network without being able to reach the internet.

If you want to test whether you can reach a specific server or domain (for instance, Google), you might need to make a network request, such as an AJAX or fetch request, to verify connectivity beyond the network connection itself.

For example:

function checkInternetConnectivity() {
    fetch('https://www.google.com', { method: 'HEAD', mode: 'no-cors'}).then((response) => {
        console.log("connected");
    }, (err) => {
       console.log("error: " + err); // (currently fetch failed)
    });
}
//Test
checkInternetConnectivity();

This method helps ensure that not only is the device connected to a network, but it also has access to the broader internet.