Generate url from form values using jquery/javascript

Question

I would like to generate the URL based on the form values. The problem is that when I click the submit button, I only get the partial URL up until the ?, eg. base-url/comparison?. I want the URL to have the form value concatenated to the end of base URL. How can I achieve this?

$('#generateCorrespondence').on('submit', function(e) {
  e.preventDefault(); 
  
  let id = $('#input-type').val();
  let selection = $('#selection').val();
  let method = $('#experimental-method').val();
  let resolution = $('#structure-resolution').val();
  
  if (id == 'loop_id') {
    let formAction = $('#generateCorrespondence').attr('action');
    let url = formAction + "id=" + selection;
    $('#generateCorrespondence').attr('action', url);
    
    console.log(url);
  }
});

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form class="form-horizontal col-sm-12" id="generateCorrespondence" action="base-url/comparison?">

  <div class="form-group col-sm-5">
    <label for="ife">Choose Selection Type</label>
    <select class="form-control" id="input-type">
      <option value="loop_id">loop_id</option>
      <option value="unit_id">unit_id</option>
    </select>
    <br />

    <label for="selection">Enter Selection</label>
    <input type="text" class="form-control" id="selection">
    <br />

    <label for="structure-resolution">Choose Equivalence Class Resolution Threshold</label>
    <select class="form-control" id="structure-resolution">
      <option value="4.0" selected>4.0</option>
      <option value="1.5">1.5</option>
      <option value="2.0">2.0</option>
      <option value="2.5">2.5</option>
      <option value="3.0">3.0</option>
      <option value="3.5">3.5</option>
      <option value="all">all</option>
    </select>
    <br />


    <label for="experimental-method">Choose Experimental Technique</label>
    <select class="form-control" id="experimental-method">
      <option value="all" selected>Any</option>
      <option value="xray">X-Ray</option>
      <option value="em">Cryo-EM</option>
    </select>
    <br />

    <button type="submit" id="submit_test" class="btn btn-primary">Submit</button>
  </div>
</form>