document.compatMode == "CSS1Compat"

var width = window.innerWidth;
var height = window.innerHeight;
if(typeof width != "Number"){  // IE
    width = document.compatMode == "CSS1Compat" ? document.documentElement.clientWidth : document.body.clientWidth;
    height = document.compatMode == "CSS1Compat" ? document.documentElement.clientHeight : document.body.clientHeight;
}
alert(width + "-------" + height)