test.js

window.addEventListener("documentViewerLoaded", function () {
  var elem = document.querySelector("tx-document-viewer");

  elem.shadowRoot.querySelectorAll(".formFieldDiv").forEach((formField) => {
    if (values[formField.name] === undefined) return;

    var formFieldType = formField.getAttribute("formfieldtype");
    var fieldValue = values[formField.name];

    switch (formFieldType) {
      case "checkbox":
        formField.checked = fieldValue;
        break;
      case "text":
        formField.value = fieldValue;
        break;
      case "selection":
        if (formField.nodeName === "INPUT") {
          formField.value = fieldValue;
        } else if (formField.nodeName === "SELECT") {
          formField.querySelectorAll("option").forEach((option) => {
            if (option.value === fieldValue) {
              option.selected = true;
            }
          });
        }
        break;
    }
  });
});