Using JS to detect IE less than 8

Today I spend most of my day in IE hell. After working most of the kinks of a new feature we are implementing I was still struggling with IE 7.

I decided to implement a fall back and provide an alternative experience for those still on this version of the browser.

Regretably a significant amount of traffic is still coming from IE 7 users to our application and we can’t just ignore it.

Since this is an embedded widget I needed it to be fully implemented on JavaScript.

The script is fairly simple, but some of the scripts on-line fail in either IE9 or IE10, so the reason to post this one here.

First, detecting IE is as easy as checking for document.all

The tricky part was to detect anythin less than IE 8. My first attempt was to use !document.querySelector but this only works in standard compliant mode or you will get false positives.

The solution was to check for (document.documentMode === undefined) this works fine in IE8, 9 and 10.

  
    if (document.all && (document.documentMode === undefined)) {
      alert("I'm sorry but you are using IE7");
      return;
    }