如果在页面上没有找到包含对话框的活动，则自动注销

Heres my working script which i've also found in this site and after idle time expire, alert message will pop up and it will direct to specific page.

However what I would like to do instead is after idle time expire it will call a dialog box where user can choose "Keep sign in" or "Exit" buttons.. How can set-up dialog box with javascipt and call it? Sorry I'm just a newbie. Thanks!

<script type="text/javascript">
var IDLE_TIMEOUT = 5; //seconds
var _idleSecondsCounter = 0;
document.onclick = function() {
    _idleSecondsCounter = 0;
};
document.onmousemove = function() {
    _idleSecondsCounter = 0;
};

document.onkeypress = function() {
    _idleSecondsCounter = 0;
};

window.setInterval(CheckIdleTime, 1000);

function CheckIdleTime() {
    _idleSecondsCounter++;
    var oPanel = document.getElementById("SecondsUntilExpire");
    if (oPanel)
        oPanel.innerHTML = (IDLE_TIMEOUT - _idleSecondsCounter) + "";

    if (_idleSecondsCounter >= IDLE_TIMEOUT) {
        //alert("Time expired!");
        //document.location.href = "logout.html";

        CALL_A_DIALOG_BOX()



    }
}

If you can use jQuery then, Please use http://jqueryui.com/dialog/#modal-confirmation