To get the physical size of the screen (including window chrome and menubar/launcher):

var width  = window.screen.width,
    height = window.screen.height;

To get the “available” area of the screen (i.e. not including any bars on the edges of the screen, but including window chrome and other windows:

var availableArea = {
    pos: {
        x: window.screen.availLeft,
        y: window.screen.availTop
    },
    size: {
        width: window.screen.availWidth,
        height: window.screen.availHeight
    }
};

To determine the color and pixel depths of the screen:

var pixelDepth = window.screen.pixelDepth,
    colorDepth = window.screen.colorDepth;

Get the window height and width

var width = window.innerWidth
var height = window.innerHeight

To get current page width and height (for any browser), e.g. when programming responsiveness:

function pageWidth() {
  return window.innerWidth != null? window.innerWidth : document.documentElement && document.documentElement.clientWidth ? document.documentElement.clientWidth : document.body != null ? document.body.clientWidth : null;
}

function pageHeight() {
  return  window.innerHeight != null? window.innerHeight : document.documentElement && document.documentElement.clientHeight ? document.documentElement.clientHeight : document.body != null? document.body.clientHeight : null;
}