How to update List item Managed Metadata Column with JSOM

I have simple list with one title column and one Metadata Column, and iam trying to update my list item but getting an error:

I found this article on google, and i have tried to follow it by implementing JSOM to update my List item. Error iam getting is when context.executeQueryAsync:

Error: Invalid field or parameter url.

 function execRequest() {
        var taxPickerIndex = $("#taxPickerOpenSingle").val();
        var result = $.parseJSON(taxPickerIndex);
        var listTitle = "GNTiles";
        var taxFieldName = "Process";
        var termId = result[0].Id;
        var term = result[0].Name;
        console.log("Term ID: " + termId);
        console.log(result);

        //var context = new SP.ClientContext(appWebUrl);
        var factory = new SP.ProxyWebRequestExecutorFactory(appWebUrl);
        context.set_webRequestExecutorFactory(factory);
        var appContextSite = new SP.AppContextSite(context, spHostUrl);
        var list = appContextSite.get_web().get_lists().getByTitle(listTitle);
        var item = list.getItemById(tileId);
        var field = list.get_fields().getByInternalNameOrTitle(taxFieldName);
        var txField = context.castTo(field, SP.Taxonomy.TaxonomyField);

        context.load(field);
        context.load(txField);
        context.load(item);

        context.executeQueryAsync(
           function () {
               var termSetId = txField.get_termSetId().toString();
               var termId;

               getTermIdForTerm(function success(id) {
                   //termId = id;
                   console.log("Kommer hit...<");
                   var termValue = new SP.Taxonomy.TaxonomyFieldValue();
                   termValue.set_label(term);
                   termValue.set_termGuid(termId);
                   termValue.set_wssId(-1);
                   txField.setFieldValueByValue(item, termValue);

                   item.update();
                   context.executeQueryAsync(
                      function () {
                          console.log('field updated');
                      }, function (sender, args) {
                          console.log(args.get_message() + '\n' + args.get_stackTrace());
                      });
               }, function (sender, args) {
                   console.log(args.get_message() + '\n' + args.get_stackTrace());
               }, context, term, termSetId);

           }, function error(err) {
               console.log(err.get_message());
           });
    }

    function getTermIdForTerm(success, error, clientContext, term, termSetId) {
        var termId = "";
        console.log("hmm");
        var tSession = SP.Taxonomy.TaxonomySession.getTaxonomySession(clientContext);
        var ts = tSession.getDefaultSiteCollectionTermStore();
        var tset = ts.getTermSet(termSetId);
        var lmi = new SP.Taxonomy.LabelMatchInformation(clientContext);

        lmi.set_lcid(1033);
        lmi.set_trimUnavailable(true);
        lmi.set_termLabel(term);

        var termMatches = tset.getTerms(lmi);

        clientContext.load(tSession);
        clientContext.load(ts);
        clientContext.load(tset);
        clientContext.load(termMatches);

        context.executeQueryAsync(
          function () {

              if (termMatches && termMatches.get_count() > 0)
                  termId = termMatches.get_item(0).get_id().toString();
              success(termId);

          }, function (sender, args) {
              console.log(args.get_message() + '\n' + args.get_stackTrace());
          });


    }

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