2 files changed, 20 insertions, 1 deletions
diff --git a/packages/client/src/scripts/clone.ts b/packages/client/src/scripts/clone.ts
new file mode 100644
index 0000000000..16fad24129
--- /dev/null
+++ b/packages/client/src/scripts/clone.ts
@@ -0,0 +1,18 @@
+// structredCloneが遅いため
+// SEE: http://var.blog.jp/archives/86038606.html
+
+type Cloneable = string | number | boolean | null | { [key: string]: Cloneable } | Cloneable[];
+
+export function deepClone<T extends Cloneable>(x: T): T {
+	if (typeof x === 'object') {
+		if (x === null) return x;
+		if (Array.isArray(x)) return x.map(deepClone) as T;
+		const obj = {} as Record<string, Cloneable>;
+		for (const [k, v] of Object.entries(x)) {
+			obj[k] = deepClone(v);
+		}
+		return obj as T;
+	} else {
+		return x;
+	}
+}
diff --git a/packages/client/src/scripts/theme.ts b/packages/client/src/scripts/theme.ts
index 3f55d9ae86..62a2b9459a 100644
--- a/packages/client/src/scripts/theme.ts
+++ b/packages/client/src/scripts/theme.ts
@@ -13,6 +13,7 @@ export type Theme = {
 
 import lightTheme from '@/themes/_light.json5';
 import darkTheme from '@/themes/_dark.json5';
+import { deepClone } from './clone';
 
 export const themeProps = Object.keys(lightTheme.props).filter(key => !key.startsWith('X'));
 
@@ -60,7 +61,7 @@ export function applyTheme(theme: Theme, persist = true) {
 	const colorSchema = theme.base === 'dark' ? 'dark' : 'light';
 
 	// Deep copy
-	const _theme = JSON.parse(JSON.stringify(theme));
+	const _theme = deepClone(theme);
 
 	if (_theme.base) {
 		const base = [lightTheme, darkTheme].find(x => x.id === _theme.base);