user_engagement_1.js

<form id="myForm">
  Name: <input type="text" name="name" id="name" /><br/>
  Email: <input type="text" name="email" id="email" /><br/>
  Password: <input type="text" name="password" id="password" /><br/>
  Website: <input type="text" name="website" id="website" /><br/>
  <button type="submit" onClick="trackUserEngagement('myForm');">Submit</button>
</form>

<script type="text/javascript">
  // Track user engagement on a form
  function trackUserEngagement(formId) {

    // Loop through all the text boxes in the form
    $( "form#" + formId + " :input" ).each( function () {

      var
        id    = $(this).attr('id'),   // ID of the textbox
        value = $(this).val();        // Value inside the text box

      // If there's something in the textbox push a tracking event to Google Analytics
      if (value.length > 0) {
        _gaq.push([ '_trackEvent', 'Forms:' + formId, 'Interacted with', id ]);
      }

    });
  }
</script>

user_engagement_2.js

<form id="myForm">
  Name:     <input type="text" name="name" id="name" data-ga-label="name" /><br/>
  Email:    <input type="text" name="email" id="email" data-ga-label="email" /><br/>
  Password: <input type="text" name="password" id="password" data-ga-label="password" /><br/>
  Website:  <input type="text" name="website" id="website" data-ga-label="website" /><br/>
  <button type="submit">Submit</button>
</form>

<script type="text/javascript">
  var _gaq = [];
  $(function() {
    $('input[data-ga-label]').each( function () {
      $(this).click( function (e) {

        var
          formId  = $(this).closest('form').attr('id');
          id      = $(this).attr('id'),       // ID of the textbox
          value   = $(this).val();            // Value inside the text box

        // Push a tracking event to Google Analytics
        _gaq.push([ '_trackEvent', 'Forms:' + formId, 'Interacted with', id ]);

      });
    });
  });
</script>

user_engagement_3.js

<form id="myForm">
  Name:     <input type="text" name="name" id="name" data-ga-label="name" /><br/>
  Email:    <input type="text" name="email" id="email" data-ga-label="email" /><br/>
  Password: <input type="text" name="password" id="password" data-ga-label="password" /><br/>
  Website:  <input type="text" name="website" id="website" data-ga-label="website" /><br/>
  <button type="submit">Submit</button>
</form>

<script type="text/javascript">
  var _gaq = [];
  $(function() {

    $('input[data-ga-label]').each( function () {

      // Binds the anonymous function to both click and blur
      // to capture clicking and tabbing into the text box.
      $(this).bind('click blur', function (e) {

        var
          formId  = $(this).closest('form').attr('id');
          id      = $(this).attr('id'),       // ID of the textbox
          value   = $(this).val();            // Value inside the text box

        // Push a tracking event to Google Analytics
        _gaq.push([ '_trackEvent', 'Forms:' + formId, 'Interacted with', id ]);
      });
    });

  });
</script>