// JavaScript Document
var subWindow;
function openWindow(url) {
  if (!subWindow || subWindow.closed) {
    var width  = 900;
    var height = 665;
    // Mendapatkan posisi kiri atas (dari layar)
    var left   = parseInt((screen.availWidth/2) - (width/2));
    var top    = parseInt((screen.availHeight/2) - (height/2));
    // Menetapkan fitur window
    var fitur  = "width=" + width + ", height=" +
        height + ", resizable=0, scrollbars=yes, left=" +
        left + ",top=" + top + ",screenX=" +
        left + ",screenY=" + top;
    // Membuka window
    subWindow  = window.open(url, "sub", fitur);
  } else {
    // Sub window sudah dibuka, sehingga tinggal
    // memberinya fokus
    subWindow.focus();
  }
}
// JavaScript Document