How to open maximized window with Javascript?

var params = [
    'height='+screen.height,
    'width='+screen.width,
    'fullscreen=yes' // only works in IE, but here for completeness
].join(',');
     // and any other options from
     // https://developer.mozilla.org/en/DOM/window.open

var popup = window.open('http://www.google.com', 'popup_window', params); 
popup.moveTo(0,0);

Please refrain from opening the popup unless the user really wants it, otherwise they will curse you and blacklist your site. ;-)

edit: Oops, as Joren Van Severen points out in a comment, this may not take into account taskbars and window decorations (in a possibly browser-dependent way). Be aware. It seems that ignoring height and width (only param is fullscreen=yes) seems to work on Chrome and perhaps Firefox too; the original 'fullscreen' functionality has been disabled in Firefox for being obnoxious, but has been replaced with maximization. This directly contradicts information on the same page of https://developer.mozilla.org/en/DOM/window.open which says that window-maximizing is impossible. This 'feature' may or may not be supported depending on the browser.

 window.open('your_url', 'popup_name','height=' + screen.height + ',width=' + screen.width + ',resizable=yes,scrollbars=yes,toolbar=yes,menubar=yes,location=yes')

The best solution I could find at present time to open a window maximized is (Internet Explorer 11, Chrome 49, Firefox 45):

  var popup = window.open("your_url", "popup", "fullscreen");
  if (popup.outerWidth < screen.availWidth || popup.outerHeight < screen.availHeight)
  {
    popup.moveTo(0,0);
    popup.resizeTo(screen.availWidth, screen.availHeight);
  }

see https://jsfiddle.net/8xwocrp6/7/

Note 1: It does not work on Edge (13.1058686). Not sure whether it's a bug or if it's as designed (I've filled a bug report, we'll see what they have to say about it). Here is a workaround:

if (navigator.userAgent.match(/Edge\/\d+/g))
{
    return window.open("your_url", "popup", "width=" + screen.width + ",height=" + screen.height);
}

Note 2: moveTo or resizeTo will not work (Access denied) if the window you are opening is on another domain.

If I use Firefox then screen.width and screen.height works fine but in IE and Chrome they don't work properly instead it opens with the minimum size.

And yes I tried giving too large numbers too like 10000 for both height and width but not exactly the maximized effect.