Uncaught TypeError: Cannot read properties of undefined (reading 'indexOf') in addActiveClass function

Question

I'm encountering a JavaScript error in my web application. I'm getting an "Uncaught TypeError: Cannot read properties of undefined (reading 'indexOf')" error on line 2 of vendor.bundle.base.js.

The call stack indicates the error might be originating from the addActiveClass function defined in template.js on line 16. This function seems to be using the indexOf method on a variable that's undefined.

Here's the relevant part of the call stack:

Uncaught TypeError: Cannot read properties of undefined (reading 'indexOf')
    at addActiveClass (template.js:16:33)
    at HTMLAnchorElement.<anonymous> (template.js:41:7)
    at Function.each (vendor.bundle.base.js:2:2976)
    at S.fn.init.each (vendor.bundle.base.js:2:1454)
    at HTMLDocument.<anonymous> (template.js:39:29)
    at e (vendor.bundle.base.js:2:30005)
    at t (vendor.bundle.base.js:2:30307)

Code Snippets:

 var masterTagSearchUrl = '@Url.Action("FindSteelTags", "Session")';
 $('#ScannedCoil_TagNo').typeahead({
     source: function (typeahead, query) {
         $.ajax({
             url: masterTagSearchUrl,
             type: "POST",
             data: { searchText: request, maxResults: 10, classCodeId: 0 },
             dataType: "JSON",
             async: false,
             success: function (results) {
                 var manufacturers = new Array;
                 $.map(results, function (data, item) {
                     var group;
                     group = {
                         SteelId: data.SteelId,
                         TagNumber: data.TagNumber
                     };
                     manufacturers.push(group);
                 });
                 typeahead.process(manufacturers);
             }
         });
     },
     property: 'name', 
     onselect: function (obj) {

     }
 });

I'm trying to implement a real-time typeahead functionality where suggestions appear as the user types in a search bar. This error seems to be preventing that functionality from working correctly.