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

I made a convenient underscore mixin for this.

_.isIE();        // Any version of IE?
_.isIE(9);       // IE 9?
_.isIE([7,8,9]); // IE 7, 8 or 9?

_.mixin({
  isIE: function(mixed) {
    if (_.isUndefined(mixed)) {
      mixed = [7, 8, 9, 10, 11];
    } else if (_.isNumber(mixed)) {
      mixed = [mixed];
    }
    for (var j = 0; j < mixed.length; j++) {
      var re;
      switch (mixed[j]) {
        case 11:
          re = /Trident.*rv\:11\./g;
          break;
        case 10:
          re = /MSIE\s10\./g;
          break;
        case 9:
          re = /MSIE\s9\./g;
          break;
        case 8:
          re = /MSIE\s8\./g;
          break;
        case 7:
          re = /MSIE\s7\./g;
          break;
      }

      if (!!window.navigator.userAgent.match(re)) {
        return true;
      }
    }

    return false;
  }
});

console.log(_.isIE());
console.log(_.isIE([7, 8, 9]));
console.log(_.isIE(11));