js判断移动端跳转代码（替换www为m）方法

if(window!=top){top.location.href=_window.location.href;}
var shouji = navigator.userAgent.match(/Android|iPad|iPhone|iPod/i) != null;
var url = _window.location.href;
var host = _window.location.host;
if(shouji){
 if(url.indexOf('//www.') > -1){
  var wwwurl = url.replace("//www.","//m.");
  location.href= wwwurl;
 }
}else{
 if(url.indexOf('//m.') > -1){
  var wwwurl = url.replace("//m.","//www.");
  location.href= wwwurl;
 }
}