可能有其它缺陷，不過正常能用

<script type="text/javascript">
function detectMobile() {
    return navigator.userAgent.match(/Android/i)
                    || navigator.userAgent.match(/webOS/i)
                    || navigator.userAgent.match(/iPhone/i)
                    || navigator.userAgent.match(/BlackBerry/i
 
)
                    || navigator.userAgent.match(/Windows Phone/i);
}


if (navigator.userAgent.match(/iPad/i)) {
   //iPad裝置
}


if (detectMobile()) {
   //移動裝置
}else{
   //PC
}
</script>