How Can I Detect Firefox Versions 3 or 4 Using JavaScript?

Browser Version Detection

Problem:
How can you determine the version of a visitor's browser in JavaScript, specifically for Firefox versions 3 or 4?

Solution:

To detect a browser's version, rather than just its type, you can utilize JavaScript's navigator.userAgent property. This property contains a string with information about the browser, including the version number.

The following code snippet exemplifies a function that analyzes the navigator.userAgent string and extracts the browser version:

navigator.sayswho = (function () {
  var ua = navigator.userAgent;
  var tem;
  var 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 'IE ' + (tem[1] || '');
  }
  if (M[1] === 'Chrome') {
    tem = ua.match(/\b(OPR|Edge)\/(\d+)/);
    if (tem != null) return tem.slice(1).join(' ').replace('OPR', 'Opera');
  }
  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 M.join(' ');
})();

console.log(navigator.sayswho); // outputs: `Chrome 62`

This function identifies and logs the browser version, which can be utilized for testing or logging purposes, enabling you to distinguish between different browser versions.

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