您可以尝试以下方法:
function getViewport() {
 var viewPortWidth;
 var viewPortHeight;
 
 if (typeof window.innerWidth != 'undefined') {
   viewPortWidth = window.innerWidth,
   viewPortHeight = window.innerHeight
 }
 else if (typeof document.documentElement != 'undefined'
 && typeof document.documentElement.clientWidth !=
 'undefined' && document.documentElement.clientWidth != 0) {
    viewPortWidth = document.documentElement.clientWidth,
    viewPortHeight = document.documentElement.clientHeight
 }
 
 else {
   viewPortWidth = document.getElementsByTagName('body')[0].clientWidth,
   viewPortHeight = document.getElementsByTagName('body')[0].clientHeight
 }
 return [viewPortWidth, viewPortHeight];
}
(http://andylangton.co.uk/articles/javascript/get-viewport-size-javascript/)
但是,甚至不可能在所有浏览器中都获得视口信息(例如,古怪模式下的IE6)。但是上面的脚本应该做得很好:-)