浏览器内核判断

let agent = navigator.userAgent.toLowerCase(),

  regStr_ie =/msie [\d.]+;/gi,

  regStr_ff =/firefox\/[\d.]+/gi,

  regStr_chrome =/chrome\/[\d.]+/gi,

  regStr_saf =/safari\/[\d.]+/gi,

  regStr_ie11 =/trident\/[\d.]+/gi,

  regStr_edge =/edge\/[\d.]+/gi,

  browserInfo ="";

//IE11以下

if (agent.indexOf("msie") >0) {

    browserInfo = agent.match(regStr_ie);

}

//firefox

if (agent.indexOf("firefox") >0) {

    browserInfo = agent.match(regStr_ff);

}

//Safari

if (agent.indexOf("safari") >0 && agent.indexOf("chrome") <0) {

    browserInfo = agent.match(regStr_saf);

}

//Chrome

if (agent.indexOf("chrome") >0) {

    browserInfo = agent.match(regStr_chrome);

}

//ie11

if (agent.indexOf("trident") >0) {

    browserInfo = agent.match(regStr_ie11);

}

//edge

if(agent.indexOf('edge') >0){

    browserInfo = agent.match(regStr_edge);

}

if (browserInfo !=='' && browserInfo.length >0) {

  let browserArray = browserInfo[0].split("\/"),

      browserName = browserArray[0],

      browserVersion = browserArray[1],

      reg =/^(chrome|firefox)$/,

      regExpMatchArray = browserName.match(reg);

  if (regExpMatchArray ==null) {

    alert('请升级浏览器');

  } else {

    let browserVersionArray = browserVersion.split("."), 

    versionFirst = browserVersionArray[0];

    versionFirst <=50?alert('请升级浏览器')：‘’；

  }

}