方法一

const detectDeviceType = () => /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ? "Mobile" : "Desktop"; 
// Example 
detectDeviceType(); // "Mobile" or "Desktop"

方法二

function browserRedirect() { 
	var sUserAgent= navigator.userAgent.toLowerCase(); 
	var bIsIpad= sUserAgent.match(/ipad/i) == "ipad"; 
	var bIsIphoneOs= sUserAgent.match(/iphone os/i) == "iphone os"; 
	var bIsMidp= sUserAgent.match(/midp/i) == "midp"; 
	var bIsUc7= sUserAgent.match(/rv:1.2.3.4/i) == "rv:1.2.3.4"; 
	var bIsUc= sUserAgent.match(/ucweb/i) == "ucweb"; 
	var bIsAndroid= sUserAgent.match(/android/i) == "android"; 
	var bIsCE= sUserAgent.match(/windows ce/i) == "windows ce"; 
	var bIsWM= sUserAgent.match(/windows mobile/i) == "windows mobile"; 
	if (bIsIpad || bIsIphoneOs || bIsMidp || bIsUc7 || bIsUc || bIsAndroid || bIsCE || bIsWM) { 
		console.log('手机端')
		window.location.href= '手机站链接'; 
	} else { 
		console.log('电脑端')
		window.location= 'PC站链接'; //亲测，如果是在PC的head中添加的话，此处为空！
	} 
} 

browserRedirect();

方三

//平台、设备和操作系统
var system ={
	win : false,
	mac : false,
	xll : false
};
//检测平台
var p = navigator.platform;
system.win = p.indexOf("Win") == 0;
system.mac = p.indexOf("Mac") == 0;
system.x11 = (p == "X11") || (p.indexOf("Linux") == 0);
//跳转语句，如果是手机访问就自动跳转到wap.baidu.com页面
if(system.win||system.mac||system.xll){
}else{
window.location.href="手机站链接";
}