如何基于js判断浏览器版本

function getBrowserType(){
  var userAgent = navigator.userAgent; //取得浏览器的userAgent字符串
  var browser='unknown';
  if (userAgent.indexOf("IE")!=-1) {
    browser="IE";
  }else if(userAgent.indexOf('Firefox')!=-1){
    browser="Firefox";
  }else if(userAgent.indexOf('OPR')!=-1){
    browser="Opera";
  }else if(userAgent.indexOf('Chrome')!=-1){
    browser="Chrome";
  }else if(userAgent.indexOf('Safari')!=-1){
    browser="Safari";
  }else if(userAgent.indexOf('Trident')!=-1){
    browser='IE 11';
  }
  return browser;
}

// 获取IE版本
function IEVersion() {
  // 取得浏览器的userAgent字符串
  var userAgent = navigator.userAgent;
  // 判断是否为小于IE11的浏览器
  var isLessIE11 = userAgent.indexOf('compatible') > -1 && userAgent.indexOf('MSIE') > -1;
  // 判断是否为IE的Edge浏览器
  var isEdge = userAgent.indexOf('Edge') > -1 && !isLessIE11;
  // 判断是否为IE11浏览器
  var isIE11 = userAgent.indexOf('Trident') > -1 && userAgent.indexOf('rv:11.0') > -1;
  if (isLessIE11) {
    var IEReg = new RegExp('MSIE (\\d+\\.\\d+);');
    // 正则表达式匹配浏览器的userAgent字符串中MSIE后的数字部分，，这一步不可省略！！！
    IEReg.test(userAgent);
    // 取正则表达式中第一个小括号里匹配到的值
    var IEVersionNum = parseFloat(RegExp['$1']);
    if (IEVersionNum === 7) {
      // IE7
      return 7
    } else if (IEVersionNum === 8) {
      // IE8
      return 8
    } else if (IEVersionNum === 9) {
      // IE9
      return 9
    } else if (IEVersionNum === 10) {
      // IE10
      return 10
    } else {
      // IE版本<7
      return 6
    }
  } else if (isEdge) {
    // edge
    return 'edge'
  } else if (isIE11) {
    // IE11
    return 11
  } else {
    // 不是ie浏览器
    return -1
  }
}

function getBroswerAndVersion(){
  var os = navigator.platform; 
  var userAgent = navigator.userAgent; 
  var info = ""; 
  var tempArray = ""; 
  //判断浏览器版本
  var isOpera = userAgent.indexOf("Opera") > -1; //判断是否Opera浏览器
  var isIE = userAgent.indexOf("compatible") > -1 && userAgent.indexOf("MSIE") > -1 && !isOpera; //判断是否IE浏览器
  var isEdge = userAgent.toLowerCase().indexOf("edge") > -1 && !isIE; //判断是否IE的Edge浏览器
  var isIE11 = (userAgent.toLowerCase().indexOf("trident") > -1 && userAgent.indexOf("rv") > -1); 

  if (/[Ff]irefox(\/\d+\.\d+)/.test(userAgent)) { 
    tempArray = /([Ff]irefox)\/(\d+\.\d+)/.exec(userAgent); 
    info += tempArray[1] + tempArray[2]; 
  } else if (isIE) { 

    var version = ""; 
    var reIE = new RegExp("MSIE (\\d+\\.\\d+);"); 
    reIE.test(userAgent); 
    var fIEVersion = parseFloat(RegExp["$1"]); 
    if (fIEVersion == 7) 
    { version = "IE7"; } 
    else if (fIEVersion == 8) 
    { version = "IE8"; } 
    else if (fIEVersion == 9) 
    { version = "IE9"; } 
    else if (fIEVersion == 10) 
    { version = "IE10"; } 
    else 
    { version = "0" } 

    info += version; 

  } else if (isEdge) { 
    info += "Edge"; 
  } else if (isIE11) { 
    info += "IE11"; 
  } else if (/[Cc]hrome\/\d+/.test(userAgent)) { 
    tempArray = /([Cc]hrome)\/(\d+)/.exec(userAgent); 
    info += tempArray[1] + tempArray[2]; 
  } else if (/[Vv]ersion\/\d+\.\d+\.\d+(\.\d)* *[Ss]afari/.test(userAgent)) { 
    tempArray = /[Vv]ersion\/(\d+\.\d+\.\d+)(\.\d)* *([Ss]afari)/.exec(userAgent); 
    info += tempArray[3] + tempArray[1]; 
  } else if (/[Oo]pera.+[Vv]ersion\/\d+\.\d+/.test(userAgent)) { 
    tempArray = /([Oo]pera).+[Vv]ersion\/(\d+)\.\d+/.exec(userAgent); 
    info += tempArray[1] + tempArray[2]; 
  } else { 
    info += "unknown"; 
  } 
  return info;
}

<!--[if lte IE 9]>
<script>
  var bro = getBroswerAndVersion();
  if(bro=="IE5" || bro=="IE6" || bro=="IE7" || bro=="IE8" ){
    alert("浏览器版本过低!请升级至IE9以上");
  }
</script>
<![endif]-->