How to preselect an option from a dropdown menu with JavaScript

window.addEventListener('DOMContentLoaded', function() {
  // find the "Department" dropdown element
  var departmentDropdown = document.querySelector('select[name="input_11"]');
  departmentDropdown.value = 'value of option with spaces';
});

The eventListener for DOMContentLoaded is optional, it’s preferable to simply load the JavaScript in the footer.

If you are familiar with Gravity Forms, you will see this is a Gravity Forms class, but as long as you select the dropdown with its class or ID, it should work the same for any dropdown.