title: Sending 2 dimensional array through formData using jQuery ajax to python flask
body: <p>I have a form which I need to add some variables to before sending it to the server which is python flask.
  I used the following code to send the form which works fine except when sending 2 dimensional array it will treat it as 1 dimensional in flask</p>
  
  <p>javascript:</p>
  
  <pre><code>form = document.getElementById('calculator-form');
  fdata = new FormData(form);
  fdata.append('readings', plotData.readings);
  $.ajax({
      url: "some/url/",
      type: 'POST',
      data: fdata,
      processData: false,
      contentType: false,
  });
  </code></pre>
  
  <p>so if <code>plotData.readings=[[1,2,3],[4,5,6]]</code>
  I receive it in flask <code>1,2,3,4,5,6</code> and I don't always know the size of the array to reshape it from flask, is there a way to send so that the backend see it as 2 dimensional array?</p>