javascript - Populate an input with the contents of a custom option (data-) attribute

Question

In the example below, I'm trying to populate an input with the contents of the option.data-foo attribute. I feel like this close... but I've got something back-to-front somewhere... Any thoughts?

---

My code :

function updateText(type) {
    var id = type+'Text';
    document.getElementById(id).data-foo = document.getElementById(type).value;
}

<form id="example" name="example">
    <select id="sensor" onchange="updateText('sensor')">
        <option value="Jval" data-foo="Jfoo">Joption</option>
        <option value="Kval" data-foo="Kfoo">Koption</option>
    </select>

    <br />
    <input type="text" value="" id="sensorText" />
</form>

Answer 1

If you're using jQuery then use this:

$('#sensor').change(function() {
  $('#sensorText').val( $(this).find('option:selected').data('foo') )
})

$('#sensor').change(function() {
  $('#sensorText').val( $(this).find('option:selected').data('foo') )
})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<form id="example" name="example">
  <select id="sensor">
    <option value="Jval" data-foo="Jfoo">Joption</option>
    <option value="Kval" data-foo="Kfoo">Koption</option>
  </select>

  <br />
  <input type="text" value="" id="sensorText" />
</form>