Added JSON Support and started working on jQuery docs

docs/patterns/index.rst

@@ -19,3 +19,4 @@ end of the request, the database connection is closed again.
    wtforms
    templateinheritance
    flashing
+   jquery

docs/patterns/jquery.rst

@@ -0,0 +1,59 @@
+AJAX With jQuery
+================
+
+`jQuery`_ is a small JavaScript library commonly used to simplify working
+with the DOM and JavaScript in general.  It is the perfect tool to make
+web applications more dynamic by exchanging JSON between server and
+client.
+
+.. _jQuery: http://jquery.com/
+
+Loading jQuery
+--------------
+
+In order to use jQuery, you have to download it first and place it in the
+static folder of your application and then ensure it's loaded.  Ideally
+you have a layout template that is used for all pages where you just have
+to add two script statements to your `head` section.  One for jQuery, and
+one for your own script (called `app.js` here):
+
+.. sourcecode:: html
+
+   <script type=text/javascript src="{{
+       url_for('static', filename='jquery.js') }}"></script>
+   <script type=text/javascript src="{{
+       url_for('static', filename='app.js') }}"></script>
+
+Where is My Site?
+-----------------
+
+Do you know where your application is?  If you are developing the answer
+is quite simple: it's on localhost port something and directly on the root
+of that server.  But what if you later decide to move your application to
+a different location?  For example to ``http://example.com/myapp``?  On
+the server side this never was a problem because we were using the handy
+:func:`~flask.url_for` function that did could answer that question for
+us, but if we are using jQuery we should better not hardcode the path to
+the application but make that dynamic, so how can we do that?
+
+A simple method would be to add a script tag to our page that sets a
+global variable to the prefix to the root of the application.  Something
+like this:
+
+.. sourcecode:: html+jinja
+
+   <script type=text/javascript>
+     $SCRIPT_ROOT = {{ request.script_root|tojson|safe }};
+   </script>
+
+The ``|safe`` is necessary so that Jinja does not escape the JSON encoded
+string with HTML rules.  Usually this would be necessary, but we are
+inside a `script` block here where different rules apply.
+
+.. admonition:: Information for Pros
+
+   In HTML the `script` tag is declared `CDATA` which means that entities
+   will not be parsed.  Everything until ``</script>`` is handled as script.
+   This also means that there must never be any ``</`` between the script
+   tags.  ``|tojson`` is kindly enough to do the right thing here and
+   escape backslashes for you.