let u = navigator.userAgent, 
let isAndroid = u.indexOf(‘Android‘) > -1 || u.indexOf(‘Linux‘) > -1; //g
let isIOS = !!u.match(/\(i[^;]+;( U;)? CPU.+Mac OS X/); //ios终端
if (isAndroid) {
    //这个是安卓操作系统
}
if (isIOS) {
　　//这个是ios操作系统
}

let userAgent = navigator.userAgent;
let Agents = ["Android", "iPhone",
    "SymbianOS", "Windows Phone",
    "iPad", "iPod"];
let flag = true;
for (let i in Agents) {
    if (userAgent.indexOf(Agents[i]) > -1) {
        flag = false;
        break;
    }
}
if(flag){
　　//这个是PC端
}else{
　　//这个是M端
}