Integrated jQuery docs from #204.

Author: mitsuhiko

docs/tips.rst

@@ -90,3 +90,95 @@ that happen. You can do this via the ``shouldSendCallback`` setting:
         var sampleRate = 10;
         return (Math.random() * 100 <= sampleRate);
     }
+
+jQuery AJAX Error Reporting
+---------------------------
+
+For automatically AJAX errors from jQuery the following tip might come in
+helpful.  However depending on the type of request you might have to do
+slightly different things.
+
+Same Origin
+-----------
+
+Whenever an Ajax request completes with an error, jQuery triggers the
+``ajaxError`` event, passing the ``event`` object, the ``jqXHR`` object
+(prior to jQuery 1.5, the ``XHR`` object), and the ``settings`` object
+that was used in the creation of the request. When an HTTP error occurs,
+the fourth argument (``thrownError``) receives the textual portion of the
+HTTP status, such as "Not Found" or "Internal Server Error."
+
+You can use this event to globally handle Ajax errors:
+
+.. code-block:: javascript
+
+    $(document).ajaxError(function(event, jqXHR, ajaxSettings, thrownError) {
+        Raven.captureMessage(thrownError || jqXHR.statusText, {
+            extra: {
+                type: ajaxSettings.type,
+                url: ajaxSettings.url,
+                data: ajaxSettings.data,
+                status: jqXHR.status,
+                error: thrownError || jqXHR.statusText,
+                response: jqXHR.responseText.substring(0, 100)
+            }
+        });
+    });
+
+
+**Note:**
+
+* This handler is not called for cross-domain script and cross-domain
+  JSONP requests.
+* If ``$.ajax()`` or ``$.ajaxSetup()`` is called with the ``global``
+  option set to ``false``, the ``.ajaxError()`` method will not fire.
+* As of jQuery 1.8, the ``.ajaxError()`` method should only be attached to
+  document.
+
+
+Cross Origin
+------------
+
+Due security reasons most web browsers are not giving permissions to
+access error messages for cross domain scripts. This is not jQuery issue
+but an overall javascript limitation.
+
+Depending on your situation you have different options now:
+
+When you control the backend
+````````````````````````````
+
+If you have access to the backend system you are calling, you can set
+response headers to allow a cross domain call:
+
+.. code-block:: yaml
+
+    Access-Control-Allow-Origin: http://domain1.com, http://domain2.com
+
+Script tags have now got a new non-standard attribute called
+``crossorigin`` (`read more
+<https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script#attr-crossorigin>`_).
+The most secure value for this would be ``anonymous``. So, you'll have to
+modify your script tags to look like the following:
+
+.. code-block:: html
+
+    <script src="http://sub.domain.com/script.js" crossorigin="anonymous"></script>
+
+When you have no access to the backend
+``````````````````````````````````````
+
+If you have no access to the backend, you could try a workaround, which is
+basically adding a timeout on the Ajax call. This is however very dirty,
+and will fail on slow connection or long response time:
+
+.. code-block:: javascript
+
+    $.ajax({
+        url: 'http:/mysite/leaflet.js',
+        success: function() { ... },
+        error: function() { ... },
+        timeout: 2000, // 2 seconds timeout before error function will be called
+        dataType: 'script',
+        crossDomain: true
+    });