how to get user agent in javascript code example

Example 1: navigator.useragent

var sBrowser, sUsrAg = navigator.userAgent;

// The order matters here, and this may report false positives for unlisted browsers.

if (sUsrAg.indexOf("Firefox") > -1) {
  sBrowser = "Mozilla Firefox";
  // "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:61.0) Gecko/20100101 Firefox/61.0"
} else if (sUsrAg.indexOf("SamsungBrowser") > -1) {
  sBrowser = "Samsung Internet";
  // "Mozilla/5.0 (Linux; Android 9; SAMSUNG SM-G955F Build/PPR1.180610.011) AppleWebKit/537.36 (KHTML, like Gecko) SamsungBrowser/9.4 Chrome/67.0.3396.87 Mobile Safari/537.36
} else if (sUsrAg.indexOf("Opera") > -1 || sUsrAg.indexOf("OPR") > -1) {
  sBrowser = "Opera";
  // "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 OPR/57.0.3098.106"
} else if (sUsrAg.indexOf("Trident") > -1) {
  sBrowser = "Microsoft Internet Explorer";
  // "Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; Zoom 3.6.0; wbx 1.0.0; rv:11.0) like Gecko"
} else if (sUsrAg.indexOf("Edge") > -1) {
  sBrowser = "Microsoft Edge";
  // "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36 Edge/16.16299"
} else if (sUsrAg.indexOf("Chrome") > -1) {
  sBrowser = "Google Chrome or Chromium";
  // "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/66.0.3359.181 Chrome/66.0.3359.181 Safari/537.36"
} else if (sUsrAg.indexOf("Safari") > -1) {
  sBrowser = "Apple Safari";
  // "Mozilla/5.0 (iPhone; CPU iPhone OS 11_4 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/11.0 Mobile/15E148 Safari/604.1 980x1306"
} else {
  sBrowser = "unknown";
}

alert("You are using: " + sBrowser);

Example 2: js get browser name and platform

var nVer = navigator.appVersion;
var nAgt = navigator.userAgent;
var browserName  = navigator.appName;
var fullVersion  = ''+parseFloat(navigator.appVersion); 
var majorVersion = parseInt(navigator.appVersion,10);
var nameOffset,verOffset,ix;

// In Opera, the true version is after "Opera" or after "Version"
if ((verOffset=nAgt.indexOf("Opera"))!=-1) {
 browserName = "Opera";
 fullVersion = nAgt.substring(verOffset+6);
 if ((verOffset=nAgt.indexOf("Version"))!=-1) 
   fullVersion = nAgt.substring(verOffset+8);
}
// In MSIE, the true version is after "MSIE" in userAgent
else if ((verOffset=nAgt.indexOf("MSIE"))!=-1) {
 browserName = "Microsoft Internet Explorer";
 fullVersion = nAgt.substring(verOffset+5);
}
// In Chrome, the true version is after "Chrome" 
else if ((verOffset=nAgt.indexOf("Chrome"))!=-1) {
 browserName = "Chrome";
 fullVersion = nAgt.substring(verOffset+7);
}
// In Safari, the true version is after "Safari" or after "Version" 
else if ((verOffset=nAgt.indexOf("Safari"))!=-1) {
 browserName = "Safari";
 fullVersion = nAgt.substring(verOffset+7);
 if ((verOffset=nAgt.indexOf("Version"))!=-1) 
   fullVersion = nAgt.substring(verOffset+8);
}
// In Firefox, the true version is after "Firefox" 
else if ((verOffset=nAgt.indexOf("Firefox"))!=-1) {
 browserName = "Firefox";
 fullVersion = nAgt.substring(verOffset+8);
}
// In most other browsers, "name/version" is at the end of userAgent 
else if ( (nameOffset=nAgt.lastIndexOf(' ')+1) < 
          (verOffset=nAgt.lastIndexOf('/')) ) 
{
 browserName = nAgt.substring(nameOffset,verOffset);
 fullVersion = nAgt.substring(verOffset+1);
 if (browserName.toLowerCase()==browserName.toUpperCase()) {
  browserName = navigator.appName;
 }
}
// trim the fullVersion string at semicolon/space if present
if ((ix=fullVersion.indexOf(";"))!=-1)
   fullVersion=fullVersion.substring(0,ix);
if ((ix=fullVersion.indexOf(" "))!=-1)
   fullVersion=fullVersion.substring(0,ix);

majorVersion = parseInt(''+fullVersion,10);
if (isNaN(majorVersion)) {
 fullVersion  = ''+parseFloat(navigator.appVersion); 
 majorVersion = parseInt(navigator.appVersion,10);
}

document.write(''
 +'Browser name  = '+browserName+'<br>'
 +'Full version  = '+fullVersion+'<br>'
 +'Major version = '+majorVersion+'<br>'
 +'navigator.appName = '+navigator.appName+'<br>'
 +'navigator.userAgent = '+navigator.userAgent+'<br>'
)