webp test

htdocs/wp-content/themes/lawcarta/header.php

@@ -72,7 +72,19 @@ require_once 'inc/walker-nav-menu.php';
         </script>
     <?php endif;?>
 
-    <script src="<?= get_theme_file_uri('/assets/js/modernizr-custom.js'); ?>"></script>
+    <script>
+        function support_format_webp() {
+            var elem = document.createElement('canvas');
+            if (!!(elem.getContext && elem.getContext('2d'))) {
+                return elem.toDataURL('image/webp').indexOf('data:image/webp') == 0;
+            } else {
+                return false;
+            }
+        }
+        if (support_format_webp()) {
+            document.getElementsByTagName('html')[0].classList.add('webp')
+        }
+    </script>
 
     <?php wp_head(); ?>
 </head>