<script type="text/javascript">
    /**
    * 获取客户端信息
    */
    function getClientInfo() {
        var userAgentInfo = navigator.userAgent;
        var Agents = new Array("Android", "iPhone", "SymbianOS", "Windows Phone", "iPad", "iPod");
        var agentinfo = null;
        for (var i = 0; i < Agents.length; i++) {
            if (userAgentInfo.indexOf(Agents[i]) > 0) { agentinfo = userAgentInfo; break; }
        }
        if (agentinfo) {
            return agentinfo;
        } else {
            return "PC";
        }
    }
    //调用示例
    alert(getClientInfo());
</script>

1、pc端写 （如果是移动端跳走）

!function(){
 function params(u, p){
        var m = new RegExp("(?:&|/?)"+p+"=([^&$]+)").exec(u);
        return m ? m[1] : '';
    }
    if(/iphone|ios|android|ipod/i.test(navigator.userAgent.toLowerCase()) == true && params(location.search, "from") != "mobile"){
        location.href = 'http://m.XXX.com';
    }
}();

2、移动端写 （如果打开是pc跳走）

!function(){
   if(/iphone|ios|android|ipod/i.test(navigator.userAgent.toLowerCase()) == false){
        location.href = 'http://XXX.com';
    }
}();