Detect all Firefox versions in JS

Question

How to detect Firefox in JavaScript?
I want to detect all versions of Firefox.

Answer 1

the best solution for me:

function GetIEVersion() {
  var sAgent = window.navigator.userAgent;
  var Idx = sAgent.indexOf("MSIE");
  // If IE, return version number.
  if (Idx > 0)
    return parseInt(sAgent.substring(Idx+ 5, sAgent.indexOf(".", Idx)));

  // If IE 11 then look for Updated user agent string.
  else if (!!navigator.userAgent.match(/Trident\/7\./))
    return 11;

  else
    return 0; //It is not IE

}
if (GetIEVersion() > 0){
			 alert("This is IE " + GetIEVersion());
		}else {
			 alert("This no is IE ");
		}