Replace jQuery example with plain JavaScript

Author: msheakoski

frontend/encore/server-data.rst

@@ -16,13 +16,18 @@ Fetch this in JavaScript:
 
 .. code-block:: javascript
 
-    // jquery isn't required, but makes things simple
-    var $ = require('jquery');
-
-    $(document).ready(function() {
-        var isAuthenticated = $('.js-user-rating').data('is-authenticated');
+    document.addEventListener('DOMContentLoaded', function() {
+        var userRating = document.querySelector('.js-user-rating');
+        var isAuthenticated = userRating.dataset.isAuthenticated;
     });
 
+.. note::
+
+    When `accessing data attributes from JavaScript`_, the attribute names are
+    converted from dash-style to camelCase. For example, ``data-is-authenticated``
+    becomes ``isAuthenticated`` and ``data-number-of-reviews`` becomes
+    ``numberOfReviews``.
+
 There is no size limit for the value of the ``data-`` attributes, so you can
 store any content. In Twig, use the ``html_attr`` escaping strategy to avoid messing
 with HTML attributes. For example, if your ``User`` object has some ``getProfileData()``
@@ -33,3 +38,5 @@ method that returns an array, you could do the following:
     <div data-user-profile="{{ app.user ? app.user.profileData|json_encode|e('html_attr') : '' }}">
         <!-- ... -->
     </div>
+
+.. _`accessing data attributes from JavaScript`: https://developer.mozilla.org/en-US/docs/Learn/HTML/Howto/Use_data_attributes