From 400286fea8215544d8fa979c89a8d9e3bcc2fd51 Mon Sep 17 00:00:00 2001
From: Sebastian Markbage <sema@fb.com>
Date: Mon, 19 Apr 2021 12:42:38 -0400
Subject: [PATCH] Use string concat in renderToString

I think this might be faster. We could probably use a combination of this
technique in the stream too to lower the overhead.
---
 .../react-dom/src/server/ReactDOMLegacyServerBrowser.js   | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/packages/react-dom/src/server/ReactDOMLegacyServerBrowser.js b/packages/react-dom/src/server/ReactDOMLegacyServerBrowser.js
index 2ea0b22d10abc..e70bcacadc8db 100644
--- a/packages/react-dom/src/server/ReactDOMLegacyServerBrowser.js
+++ b/packages/react-dom/src/server/ReactDOMLegacyServerBrowser.js
@@ -38,11 +38,11 @@ function renderToString(
 ): string {
   let didFatal = false;
   let fatalError = null;
-  const result = [];
+  const result = '';
   const destination = {
     push(chunk) {
-      if (chunk) {
-        result.push(chunk);
+      if (chunk !== null) {
+        result += chunk;
       }
       return true;
     },
@@ -69,7 +69,7 @@ function renderToString(
   if (didFatal) {
     throw fatalError;
   }
-  return result.join('');
+  return result;
 }
 
 function renderToNodeStream() {