Detect IE version (prior to v9) in JavaScript

Question

I want to bounce users of our web site to an error page if they\'re using a version of Internet Explorer prior to v9. It\'s just not worth our time and money to

Answer 1

Your code can do the check, but as you thought, if someone try to access your page using IE v1 or > v19 will not get the error, so might be more safely do the check with Regex expression like this code below:

var userAgent = navigator.userAgent.toLowerCase();
// Test if the browser is IE and check the version number is lower than 9
if (/msie/.test(userAgent) && 
    parseFloat((userAgent.match(/.*(?:rv|ie)[\/: ](.+?)([ \);]|$)/) || [])[1]) < 9) {
  // Navigate to error page
}