From ed1f3ec22b5b03d314e545a818513cf4283adecb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jacob=20Gro=C3=9F?= <kurtextrem@gmail.com>
Date: Sat, 20 Jul 2024 11:13:54 +0200
Subject: [PATCH] server-islands: only encode ETAGO delimiter & opening HTML
 comment

---
 .changeset/fifty-socks-end.md                    |  5 +++++
 .../src/runtime/server/render/server-islands.ts  | 16 +++++++++++-----
 2 files changed, 16 insertions(+), 5 deletions(-)
 create mode 100644 .changeset/fifty-socks-end.md

diff --git a/.changeset/fifty-socks-end.md b/.changeset/fifty-socks-end.md
new file mode 100644
index 0000000000000..5afb9524f1d51
--- /dev/null
+++ b/.changeset/fifty-socks-end.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Only escape the script tag ETAGO delimiter and opening HTML comment syntax in server islands to reduce encoding work.
diff --git a/packages/astro/src/runtime/server/render/server-islands.ts b/packages/astro/src/runtime/server/render/server-islands.ts
index 52b6b006e1935..a3821b1034c21 100644
--- a/packages/astro/src/runtime/server/render/server-islands.ts
+++ b/packages/astro/src/runtime/server/render/server-islands.ts
@@ -14,13 +14,19 @@ export function containsServerDirective(props: Record<string | number, any>) {
 	return 'server:component-directive' in props;
 }
 
+const scriptRegex = /<\/script/gui;
+const commentRegex = /<!--/gu;
+const scriptReplacer = '<\\/script';
+const commentReplacer = '\\u003C!--';
+
+/**
+ * Encodes the script end-tag open (ETAGO) delimiter and opening HTML comment syntax for JSON inside a `<script>` tag.
+ * @see https://mathiasbynens.be/notes/etago
+ */
 function safeJsonStringify(obj: any) {
 	return JSON.stringify(obj)
-		.replace(/\u2028/g, '\\u2028')
-		.replace(/\u2029/g, '\\u2029')
-		.replace(/</g, '\\u003c')
-		.replace(/>/g, '\\u003e')
-		.replace(/\//g, '\\u002f');
+		.replace(scriptRegex, scriptReplacer)
+		.replace(commentRegex, commentReplacer);
 }
 
 export function renderServerIsland(