How to show an alert after reloading the page in JavaScript?

You can use sessionStorage:

$( "button" ).click( function () {
        sessionStorage.reloadAfterPageLoad = true;
        window.location.reload();
    } 
);

$( function () {
        if ( sessionStorage.reloadAfterPageLoad ) {
            alert( "Hello world" );
            sessionStorage.reloadAfterPageLoad = false;
        }
    } 
);

That's called onload. It came waaaaay before DOM ready was around, and DOM ready was actually created for the exact reason that onload waited on images.

window.onload = function () { 
    alert("It's loaded!");
    //dom not only ready, but everything is loaded
}

And a jQuery Javascript solution is to bind the window.onload event in document.ready().

$(window).bind("load", function() {
   // code here
});