移动端页面宽度自适应

<script type="text/javascript">
if(/Android (\d+\.\d+)/.test(navigator.userAgent)){
var version = parseFloat(RegExp.$1);
if(version>2.3){
var phoneScale = parseInt(window.screen.width)/640;
document.write('<meta name="viewport" content="width=640, minimum-scale = '+ phoneScale +', maximum-scale = '+ phoneScale +', target-densitydpi=device-dpi">');
}else{
document.write('<meta name="viewport" content="width=640, target-densitydpi=device-dpi">');
}
}else{
document.write('<meta name="viewport" content="width=640, user-scalable=no, target-densitydpi=device-dpi">');
}
//微信去掉下方刷新栏
if(navigator.userAgent.indexOf('MicroMessenger') >= 0){
document.addEventListener('WeixinJSBridgeReady', function() {
//WeixinJSBridge.call('hideToolbar');
});
}
</script>