web页面放到手机页面，缩放问题

 1 <script>
 2 ! function( userAgent ) {
 3     var screen_w = parseInt(window.screen.width),
 4         scale = screen_w / 640;
 5     if ( /Android (\d+\.\d+)/.test( userAgent ) ) {
 6         var version = parseFloat( RegExp.$1 );
 7         document.write( version > 2.3
 8             ? ‘<meta name="viewport" content="width=640, minimum-scale = ‘ + scale + ", maximum-scale = " + scale + ‘, target-densitydpi=device-dpi">‘
 9             : ‘<meta name="viewport" content="width=640, target-densitydpi=device-dpi">‘ );
10     } else {
11         document.write( ‘<meta name="viewport" content="width=640, user-scalable=no, target-densitydpi=device-dpi">‘ );
12     }
13 }( navigator.userAgent );
14 
15 
16 </script>