diff --git a/includes/bootstrap.inc b/includes/bootstrap.inc
index 490ac45..f568767 100644
--- a/includes/bootstrap.inc
+++ b/includes/bootstrap.inc
@@ -41,6 +41,16 @@ define('ERROR_REPORTING_DISPLAY_SOME', 1);
 define('ERROR_REPORTING_DISPLAY_ALL', 2);
 
 /**
+ * JS error reporting level: display errors in console.
+ */
+define('JS_ERROR_REPORTING_CONSOLE', 0);
+
+/**
+ * JS error reporting level: display errors in an alert window.
+ */
+define('JS_ERROR_REPORTING_ALERT', 1);
+
+/**
  * Indicates that the item should never be removed unless explicitly selected.
  *
  * The item may be removed using cache_clear_all() with a cache ID.
diff --git a/includes/common.inc b/includes/common.inc
index c97704c..690d4fb 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -4271,6 +4271,7 @@ function drupal_add_js($data = NULL, $options = NULL) {
           'data' => array(
             array('basePath' => base_path()),
             array('pathPrefix' => empty($prefix) ? '' : $prefix),
+            array('alertDisplay' => (int) variable_get('js_error_level', JS_ERROR_REPORTING_ALERT)),
           ),
           'type' => 'setting',
           'scope' => 'header',
diff --git a/index.php b/index.php
index 8b83199..e9007fb 100644
--- a/index.php
+++ b/index.php
@@ -19,3 +19,6 @@ define('DRUPAL_ROOT', getcwd());
 require_once DRUPAL_ROOT . '/includes/bootstrap.inc';
 drupal_bootstrap(DRUPAL_BOOTSTRAP_FULL);
 menu_execute_active_handler();
+
+$javascript = drupal_add_js(array('drupal' => 'rocks', 'dries' => 280342800), 'setting');
+print_r($javascript);
diff --git a/misc/ajax.js b/misc/ajax.js
index bb4a6e1..c7b3dc6 100644
--- a/misc/ajax.js
+++ b/misc/ajax.js
@@ -230,16 +230,16 @@ Drupal.ajax = function (base, element, element_settings) {
  * will test to see if the key press is valid to trigger this event and
  * if it is, trigger it for us and prevent other keypresses from triggering.
  * In this case we're handling RETURN and SPACEBAR keypresses (event codes 13
- * and 32. RETURN is often used to submit a form when in a textfield, and 
- * SPACE is often used to activate an element without submitting. 
+ * and 32. RETURN is often used to submit a form when in a textfield, and
+ * SPACE is often used to activate an element without submitting.
  */
 Drupal.ajax.prototype.keypressResponse = function (element, event) {
   // Create a synonym for this to reduce code confusion.
   var ajax = this;
 
   // Detect enter key and space bar and allow the standard response for them,
-  // except for form elements of type 'text' and 'textarea', where the 
-  // spacebar activation causes inappropriate activation if #ajax['keypress'] is 
+  // except for form elements of type 'text' and 'textarea', where the
+  // spacebar activation causes inappropriate activation if #ajax['keypress'] is
   // TRUE. On a text-type widget a space should always be a space.
   if (event.which == 13 || (event.which == 32 && element.type != 'text' && element.type != 'textarea')) {
     $(ajax.element_settings.element).trigger(ajax.element_settings.event);
@@ -476,7 +476,8 @@ Drupal.ajax.prototype.getEffect = function (response) {
  * Handler for the form redirection error.
  */
 Drupal.ajax.prototype.error = function (xmlhttprequest, uri, customMessage) {
-  alert(Drupal.ajaxError(xmlhttprequest, uri, customMessage));
+  Drupal.alert(Drupal.ajaxError(xmlhttprequest, uri, customMessage));
+
   // Remove the progress element.
   if (this.progress.element) {
     $(this.progress.element).remove();
diff --git a/misc/autocomplete.js b/misc/autocomplete.js
index d71441b..2b68cb6 100644
--- a/misc/autocomplete.js
+++ b/misc/autocomplete.js
@@ -310,7 +310,7 @@ Drupal.ACDB.prototype.search = function (searchString) {
         }
       },
       error: function (xmlhttp) {
-        alert(Drupal.ajaxError(xmlhttp, db.uri));
+        Drupal.alert(Drupal.ajaxError(xmlhttp, db.uri));
       }
     });
   }, this.delay);
diff --git a/misc/drupal.js b/misc/drupal.js
index 427c4a1..db3ee8c 100644
--- a/misc/drupal.js
+++ b/misc/drupal.js
@@ -414,6 +414,20 @@ Drupal.getSelection = function (element) {
 };
 
 /**
+ * Shows an error on an alert window or the console
+ */
+ Drupal.alert = function (message) {
+  if (Drupal.settings.alertDisplay) {
+    alert(message);
+  }
+  else {
+    if (typeof(window.console) !== 'undefined') {
+      window.console.log(message);
+    }
+  }
+ }
+
+/**
  * Build an error message from an Ajax response.
  */
 Drupal.ajaxError = function (xmlhttp, uri, customMessage) {
diff --git a/modules/simpletest/tests/common.test b/modules/simpletest/tests/common.test
index 92aefe4..49a4e3e 100644
--- a/modules/simpletest/tests/common.test
+++ b/modules/simpletest/tests/common.test
@@ -1420,8 +1420,8 @@ class JavaScriptTestCase extends DrupalWebTestCase {
    */
   function testAddSetting() {
     $javascript = drupal_add_js(array('drupal' => 'rocks', 'dries' => 280342800), 'setting');
-    $this->assertEqual(280342800, $javascript['settings']['data'][2]['dries'], 'JavaScript setting is set correctly.');
-    $this->assertEqual('rocks', $javascript['settings']['data'][2]['drupal'], 'The other JavaScript setting is set correctly.');
+    $this->assertEqual(280342800, $javascript['settings']['data'][3]['dries'], 'JavaScript setting is set correctly.');
+    $this->assertEqual('rocks', $javascript['settings']['data'][3]['drupal'], 'The other JavaScript setting is set correctly.');
   }
 
   /**
diff --git a/modules/system/system.admin.inc b/modules/system/system.admin.inc
index 8ef7d7c..e90b9f0 100644
--- a/modules/system/system.admin.inc
+++ b/modules/system/system.admin.inc
@@ -1676,6 +1676,17 @@ function system_logging_settings() {
     '#description' => t('It is recommended that sites running on production environments do not display any errors.'),
   );
 
+  $form['js_error_level'] = array(
+    '#type' => 'radios',
+    '#title' => t('Javascript alert behaviour'),
+    '#default_value' => variable_get('js_error_level', JS_ERROR_REPORTING_ALERT),
+    '#options' => array(
+      JS_ERROR_REPORTING_ALERT => t('Show in alert window'),
+      JS_ERROR_REPORTING_CONSOLE => t('Show in console'),
+    ),
+    '#description' => t('This applies to certain javascript errors (i.e. AJAX), allowing you to disable the alert and have them being logged to the browser console when available.'),
+  );
+
   return system_settings_form($form);
 }