jQuery获取document和window宽高的实现方法

<!DOCTYPE html>
<html>
<head>
<script src="js/jquery.min.js">
</script>
<script>
$(document).ready(function(){
 $("button").click(function(){
  var txt="";
  txt+="Document width/height: " + $(document).width();
  txt+="x" + $(document).height() + "\n";
  txt+="Window width/height: " + $(window).width();
  txt+="x" + $(window).height();
  alert(txt);
 });
});
</script>
</head>
<body>
<button>Display dimensions of document and window</button>
</body>
</html>