javaScript获取页面，屏幕等高度与宽度

//获取页面数据
 function getPageSize(){  
   var xScroll, yScroll;  
   if (window.innerHeight && window.scrollMaxY) {  
     xScroll = document.body.scrollWidth;
     yScroll = window.innerHeight + window.scrollMaxY;
   } else if (document.body.scrollHeight > document.body.offsetHeight){ // all but Explorer Mac
     xScroll = document.body.scrollWidth;
     yScroll = document.body.scrollHeight;
   } else{ // Explorer Macwould also work in Explorer 6 Strict, Mozilla and Safari
     xScroll = document.body.offsetWidth;
     yScroll = document.body.offsetHeight;
   }
   var windowWidth, windowHeight;
   if (self.innerHeight) {  // all except Explorer
     windowWidth = self.innerWidth;
     windowHeight = self.innerHeight;
   } else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
     windowWidth = document.documentElement.clientWidth;
     windowHeight = document.documentElement.clientHeight;
   } else if (document.body) { // other Explorers
     windowWidth = document.body.clientWidth;
     windowHeight = document.body.clientHeight;
   }  
   // for small pages with total height less then height of the viewport
   if(yScroll < windowHeight){
     pageHeight = windowHeight;
   } else { 
     pageHeight = yScroll;
   }
   if(xScroll < windowWidth){  
     pageWidth = windowWidth;
   } else {