Test If A Site Is Up Or Down

JavaScript does not allow you to do cross-domain call but you can test if a site is up or down using this script:

function checkServerStatus( url )
{
    var script = document.body.appendChild(document.createElement("script"));
    script.onload = function()
    {
        alert( url + " is online");
    };
    script.onerror = function()
    {
        alert( url + " is offline");
    };
    script.src = url;
}

checkServerStatus( "http://google.com" );
checkServerStatus( "http://thisdomainsurelynotexists.me" );

I found this code at https://petermolnar.eu/linux-tech-coding/test-site-javascript