add note about jquery inclusion during action

README.md

@@ -294,6 +294,20 @@ protected function init()
 }
 ```
 
+If you include jQuery during an action, you need to call `DebugBar::suppressJquery();`.
+This will move all our scripts after your own, which should include Jquery first.
+
+```php
+public function my_action()
+{
+    DebugBar::suppressJquery();
+    Requirements::javascript("//code.jquery.com/jquery-3.3.1.min.js");
+    Requirements::javascript("my.plugin.js");
+
+    return $this;
+}
+```
+
 #### FulltextSearchable support
 
 It has been reported that the `FulltextSearchable` extension conflicts with the `config_collector`.

code/DebugBar.php

@@ -62,6 +62,11 @@ class DebugBar
      */
     public static $bufferingEnabled = false;
 
+    /**
+     * @var bool
+     */
+    public static $suppressJquery = false;
+
     /**
      * @var JavascriptRenderer
      */
@@ -295,6 +300,18 @@ public static function moduleResource($path)
         return ModuleLoader::getModule('lekoala/silverstripe-debugbar')->getResource($path);
     }
 
+    public static function suppressJquery($flag = true)
+    {
+        $file = "debugbar/assets/vendor/jquery/dist/jquery.min.js";
+        if ($flag) {
+            Requirements::block($file);
+        } else {
+            Requirements::unblock($file);
+        }
+
+        self::$suppressJquery = $flag;
+    }
+
     /**
      * Include DebugBar assets using Requirements API
      * This needs to be called before the template is rendered otherwise the calls to the Requirements API are ignored

code/Middleware/DebugBarMiddleware.php

@@ -7,6 +7,7 @@
 use SilverStripe\Control\Director;
 use SilverStripe\Control\HTTPRequest;
 use SilverStripe\Control\HTTPResponse;
+use SilverStripe\Dev\Debug;
 use SilverStripe\View\Requirements;
 
 class DebugBarMiddleware implements HTTPMiddleware
@@ -102,6 +103,18 @@ protected function afterRequest(HTTPRequest $request, HTTPResponse $response)
         // Inject init script into the HTML response
         $body = (string)$response->getBody();
         if (strpos($body, '</body>') !== false) {
+            if (DebugBar::$suppressJquery) {
+                // Move scripts after the latest script
+                $matches = [];
+                preg_match_all('/<script(.*) src="(.*)\/debugbar\/(.*)"><\/script>/', $body, $matches);
+                $body = preg_replace('/<script(.*) src="(.*)\/debugbar\/(.*)"><\/script>\n/', '', $body);
+
+                $ourRequirements = array_reverse($matches[0]);
+                foreach ($ourRequirements as $ourRequirement) {
+                    $script = $ourRequirement . "\n" . $script;
+                }
+            }
+
             if (Requirements::get_write_js_to_body()) {
                 $body = str_replace('</body>', $script . '</body>', $body);
             } else {