How can you detect the version of a browser?

Question

I\'ve been searching around for code that would let me detect if the user visiting the website has Firefox 3 or 4. All I have found is code to detect the type of browser but

Answer 1

This is an improvement on Kennebec's answer.

function get_browser() {
    var ua=navigator.userAgent,tem,M=ua.match(/(opera|chrome|safari|firefox|msie|trident(?=\/))\/?\s*(\d+)/i) || []; 
    if(/trident/i.test(M[1])){
        tem=/\brv[ :]+(\d+)/g.exec(ua) || []; 
        return {name:'IE',version:(tem[1]||'')};
        }   
    if(M[1]==='Chrome'){
        tem=ua.match(/\bOPR|Edge\/(\d+)/)
        if(tem!=null)   {return {name:'Opera', version:tem[1]};}
        }   
    M=M[2]? [M[1], M[2]]: [navigator.appName, navigator.appVersion, '-?'];
    if((tem=ua.match(/version\/(\d+)/i))!=null) {M.splice(1,1,tem[1]);}
    return {
      name: M[0],
      version: M[1]
    };
 }

var browser=get_browser(); // browser.name = 'Chrome'
                           // browser.version = '40'

console.log(browser);

This way you can shield yourself from the obscurity of the code.