[jQuery] How to convert prototype to jquery

My prototype script:
function loginMenu() {
$('mydiv').innerHTML = "Loading...";
var param = Form.serialize($('myForm'));
var myAjax = new Ajax.Updater (
    'myOutputDiv',
    '<%=$app%>/users/login',
    {
        method: 'get',
        parameters: param,
        evalScripts: true
    });
return false;
}
?