⚡ Bolt: [성능 개선] i18n.js 초기화 시 불필요한 DOM 업데이트 방지

.jules/bolt.md

@@ -1,3 +1,6 @@
 ## 2024-06-20 - Unnecessary initial DOM updates for default language
 **Learning:** The simple static i18n implementation runs `node.textContent = dict[node.dataset.i18n]` for every translatable node on the initial script load, even when the HTML is already written in the target language (Korean). This creates unnecessary layout/paint operations and blocking time on the main thread for elements that don't need text changes.
 **Action:** Always check if the current value matches the desired value before updating the DOM (`node.textContent !== newText`), and add early exits when setting state to the same value to avoid redundant DOM traversal and writes.
+## 2026-06-22 - Prevent redundant DOM queries on initial language set
+**Learning:** The simple static i18n implementation was scanning the entire document to set translations even when the pre-rendered document language matched the user's preferred language. This happened because `currentLang` was initially `null`, causing the early return `if (currentLang === lang) return;` to fail on the initial page load.
+**Action:** Always initialize language state variables using existing document attributes (`document.documentElement.lang`) if available, to ensure early-return checks correctly skip redundant work when the page is already in the target state.

i18n.js

@@ -308,7 +308,7 @@ let langButtons = null;
 let metaDesc = null;
 let ogDesc = null;
 let footerLogo = null;
-let currentLang = null;
+let currentLang = document.documentElement.lang || "ko";
 
 function setLanguage(lang) {
   if (currentLang === lang) return; // Skip if already in the requested language