let isIOS = userAgent.toLowerCase().indexOf("like mac os x") > 0; //ios终端

if (isIOS) {

//ios

let regStr_saf = /os [\d._]*/gi;

let verinfo = userAgent.toLowerCase().match(regStr_saf);

var ver = (verinfo + "").replace(/[^0-9|_.]/ig, "").replace(/_/ig, ".");

alert(ver);

}