diff --git a/includes/common.inc b/includes/common.inc
index c97704c..f0d7453 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -4208,7 +4208,12 @@ function drupal_region_class($region) {
  *     dependency on jQuery, then for improved front-end performance Drupal
  *     will not add jQuery and related libraries and settings to the page.
  *   - defer: If set to TRUE, the defer attribute is set on the <script>
- *     tag. Defaults to FALSE.
+ *     tag. Defaults to FALSE. Note that setting this to TRUE will disable
+ *     preprocessing as though the 'preprocess' option was set to FALSE.
+ *   - attributes: An associative array of attributes for the <script> tag.
+ *     This may be used to add 'defer', 'async' or custom attributes. Note that
+ *     setting any attributes will disable preprocessing as though the
+ *     'preprocess' option was set to FALSE.
  *   - cache: If set to FALSE, the JavaScript file is loaded anew on every page
  *     call; in other words, it is not cached. Used only when 'type' references
  *     a JavaScript file. Defaults to TRUE.
@@ -4289,6 +4294,7 @@ function drupal_add_js($data = NULL, $options = NULL) {
           'preprocess' => TRUE,
           'cache' => TRUE,
           'defer' => FALSE,
+          'attributes' => array(),
         ),
       );
       $javascript = drupal_array_merge_deep($javascript, $default_javascript);
@@ -4339,6 +4345,7 @@ function drupal_js_defaults($data = NULL) {
     'preprocess' => TRUE,
     'version' => NULL,
     'data' => $data,
+    'attributes' => array(),
   );
 }
 
@@ -4469,7 +4476,13 @@ function drupal_get_js($scope = 'header', $javascript = NULL, $skip_alter = FALS
       case 'inline':
         $js_element = $element;
         if ($item['defer']) {
-          $js_element['#attributes']['defer'] = 'defer';
+          if (empty($item['attributes'])) {
+            $item['attributes'] = array();
+          }
+          $item['attributes']['defer'] = 'defer';
+        }
+        if (!empty($item['attributes'])) {
+          $js_element['#attributes'] += $item['attributes'];
         }
         $js_element['#value_prefix'] = $embed_prefix;
         $js_element['#value'] = $item['data'];
@@ -4479,9 +4492,12 @@ function drupal_get_js($scope = 'header', $javascript = NULL, $skip_alter = FALS
 
       case 'file':
         $js_element = $element;
-        if (!$item['preprocess'] || !$preprocess_js) {
-          if ($item['defer']) {
-            $js_element['#attributes']['defer'] = 'defer';
+        if (!$item['preprocess'] || !$preprocess_js || $item['defer'] || !empty($item['attributes'])) {
+          if (!empty($item['defer'])) {
+            $item['attributes']['defer'] = 'defer';
+          }
+          if (!empty($item['attributes'])) {
+            $js_element['#attributes'] += $item['attributes'];
           }
           $query_string_separator = (strpos($item['data'], '?') !== FALSE) ? '&' : '?';
           $js_element['#attributes']['src'] = file_create_url($item['data']) . $query_string_separator . ($item['cache'] ? $query_string : REQUEST_TIME);
@@ -4504,8 +4520,14 @@ function drupal_get_js($scope = 'header', $javascript = NULL, $skip_alter = FALS
       case 'external':
         $js_element = $element;
         // Preprocessing for external JavaScript files is ignored.
-        if ($item['defer']) {
-          $js_element['#attributes']['defer'] = 'defer';
+        if (!empty($item['defer'])) {
+          if (empty($item['attributes'])) {
+            $item['attributes'] = array();
+          }
+          $item['attributes']['defer'] = 'defer';
+        }
+        if (!empty($item['attributes'])) {
+          $js_element['#attributes'] += $item['attributes'];
         }
         $js_element['#attributes']['src'] = $item['data'];
         $processed[$index++] = theme('html_tag', array('element' => $js_element));
diff --git a/modules/simpletest/tests/common.test b/modules/simpletest/tests/common.test
index 92aefe4..2539837 100644
--- a/modules/simpletest/tests/common.test
+++ b/modules/simpletest/tests/common.test
@@ -1751,6 +1751,157 @@ class JavaScriptTestCase extends DrupalWebTestCase {
   }
 
   /**
+   * Tests adding JavaScript files with additional attributes.
+   */
+  public function testAttributes() {
+    // Disable aggregation.
+    variable_set('preprocess_js', 0);
+    // Add internal and external JavaScript files that add the 'async' and
+    // 'defer' attributes, and check that these attributes appear on the
+    // <script> tags.
+    $js_internal = 'misc/collapse.js';
+    $js_external = 'http://example.com/script.js';
+    drupal_add_js($js_internal, array('attributes' => array('async' => 'async'), 'defer' => 'defer'));
+    drupal_add_js($js_external, array(
+      'attributes' => array(
+        'async' => 'async',
+      ),
+      'defer' => 'defer',
+      'type' => 'external',
+    ));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @async="async" and @defer="defer"]'), 'Rendered internal JavaScript with correct defer and async attributes.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @async="async" and @defer="defer"]'), 'Rendered external JavaScript with correct defer and async attributes.');
+
+    // Only 'defer' attribute is set.
+    drupal_add_js($js_internal, array('defer' => 'defer'));
+    drupal_add_js($js_external, array('defer' => 'defer', 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @defer="defer"]'), 'Rendered internal JavaScript with correct defer attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @defer="defer"]'), 'Rendered external JavaScript with correct defer attribute.');
+
+    // Only 'async' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('async' => 'async')));
+    drupal_add_js($js_external, array('attributes' => array('async' => 'async'), 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @async="async"]'), 'Rendered internal JavaScript with correct async attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @async="async"]'), 'Rendered external JavaScript with correct async attribute.');
+
+    // Only 'custom' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('custom' => 'foo')));
+    drupal_add_js($js_external, array('attributes' => array('custom' => 'foo'), 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @custom="foo"]'), 'Rendered internal JavaScript with correct custom attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @custom="foo"]'), 'Rendered external JavaScript with correct custom attribute.');
+
+    // Only 'defer' and 'custom' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('custom' => 'foo'), 'defer' => 'defer'));
+    drupal_add_js($js_external, array(
+      'attributes' => array(
+        'custom' => 'foo',
+      ),
+      'defer' => 'defer',
+      'type' => 'external',
+    ));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @custom="foo" and @defer="defer"]'), 'Rendered internal JavaScript with correct custom attribute and defer attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @custom="foo" and @defer="defer"]'), 'Rendered external JavaScript with correct custom attribute and defer attribute.');
+
+    // Only 'async' and 'custom' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('custom' => 'foo', 'async' => 'async')));
+    drupal_add_js($js_external, array(
+      'attributes' => array(
+        'custom' => 'foo',
+        'async' => 'async',
+      ),
+      'type' => 'external',
+    ));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @custom="foo" and @async="async"]'), 'Rendered internal JavaScript with custom attribute and async attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @custom="foo" and @async="async"]'), 'Rendered external JavaScript with correct custom attribute and async attribute.');
+  }
+
+  /**
+   * Tests that attributes are maintained when JS aggregation is enabled.
+   */
+  public function testAggregatedAttributes() {
+    // Enable aggregation.
+    variable_set('preprocess_js', TRUE);
+
+    // Add internal and external JavaScript files that add the 'async' and
+    // 'defer' attributes, and check that these attributes appear on the
+    // <script> tags.
+    $js_internal = 'misc/collapse.js';
+    $js_external = 'http://example.com/script.js';
+    drupal_add_js($js_internal, array('attributes' => array('async' => 'async'), 'defer' => 'defer'));
+    drupal_add_js($js_external, array('attributes' => array('async' => 'async'), 'defer' => 'defer', 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @async="async" and @defer="defer"]'), 'Rendered internal JavaScript with correct defer and async attributes.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @async="async" and @defer="defer"]'), 'Rendered external JavaScript with correct defer and async attributes.');
+
+    // Only 'defer' attribute is set.
+    drupal_add_js($js_internal, array('defer' => 'defer'));
+    drupal_add_js($js_external, array('defer' => 'defer', 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @defer="defer"]'), 'Rendered internal JavaScript with correct defer attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @defer="defer"]'), 'Rendered external JavaScript with correct defer attribute.');
+
+    // Only 'async' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('async' => 'async')));
+    drupal_add_js($js_external, array('attributes' => array('async' => 'async'), 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @async="async"]'), 'Rendered internal JavaScript with correct async attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @async="async"]'), 'Rendered external JavaScript with correct async attribute.');
+
+    // Only 'custom' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('custom' => 'foo')));
+    drupal_add_js($js_external, array('attributes' => array('custom' => 'foo'), 'type' => 'external'));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @custom="foo"]'), 'Rendered internal JavaScript with correct custom attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @custom="foo"]'), 'Rendered external JavaScript with correct custom attribute.');
+
+    // Only 'defer' and 'custom' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('custom' => 'foo'), 'defer' => 'defer'));
+    drupal_add_js($js_external, array(
+      'attributes' => array(
+        'custom' => 'foo',
+      ),
+      'defer' => 'defer',
+      'type' => 'external',
+    ));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @custom="foo" and @defer="defer"]'), 'Rendered internal JavaScript with custom attribute and defer attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @custom="foo" and @defer="defer"]'), 'Rendered external JavaScript with correct custom attribute and defer attribute.');
+
+    // Only 'async' and 'custom' attribute is set.
+    drupal_add_js($js_internal, array('attributes' => array('custom' => 'foo', 'async' => 'async')));
+    drupal_add_js($js_external, array(
+      'attributes' => array(
+        'custom' => 'foo',
+        'async' => 'async',
+      ),
+      'type' => 'external',
+    ));
+    $javascript = drupal_get_js();
+    $this->drupalSetContent($javascript);
+    $this->assertTrue($this->xpath('//script[starts-with(@src, "' . file_create_url($js_internal) . '") and @custom="foo" and @async="async"]'), 'Rendered internal JavaScript with custom attribute and async attribute.');
+    $this->assertTrue($this->xpath('//script[@src="' . $js_external . '" and @custom="foo" and @async="async"]'), 'Rendered external JavaScript with correct custom attribute and async attribute.');
+  }
+
+  /**
    * Test altering a JavaScript's weight via hook_js_alter().
    *
    * @see simpletest_js_alter()