Getting error in IE 11 when getting value from select?

Questions
1

Im getting an error in IE11 when I try to get the select value and it says that it is on row 980 i framwork.js

On this row in the below.
for (var i = 0; i < dom[0].selectedOptions.length; i += 1) {

function val(value) {
    var dom = this;
    if (typeof value === 'undefined') {
      if (dom[0]) {
        if (dom[0].multiple && dom[0].nodeName.toLowerCase() === 'select') {
          var values = [];
          for (var i = 0; i < dom[0].selectedOptions.length; i += 1) {
            values.push(dom[0].selectedOptions[i].value);
          }
          return values;
        }
        return dom[0].value;
      }
      return undefined;
    }

If I understand it right, IE11 cant read selectedindex or something?

Im getting the value like this.

var kategori =$$(document).find('select[id=kategori]').val()

So how can I make this to work?
Thanks a lot!