diff --git a/src-tauri/src/pake.js b/src-tauri/src/pake.js
index 89622b4..ca1b9d7 100644
--- a/src-tauri/src/pake.js
+++ b/src-tauri/src/pake.js
@@ -154,22 +154,22 @@ function setDefaultZoom() {
   }
 }
 
-function zoomCommon(callback) {
+function zoomCommon(zoomRule) {
   const htmlZoom = window.localStorage.getItem('htmlZoom') || '100%';
   const html = document.getElementsByTagName('html')[0];
-  const zoom = callback(htmlZoom);
+  const zoom = zoomRule(htmlZoom);
   html.style.zoom = zoom;
   window.localStorage.setItem('htmlZoom', zoom);
 }
 
 function zoomIn() {
   zoomCommon((htmlZoom) =>
-    parseInt(htmlZoom) < 200 ? parseInt(htmlZoom) + 10 + '%' : '200%',
+    `${Math.min(parseInt(htmlZoom) + 10, 200)}%`
   );
 }
 
 function zoomOut() {
   zoomCommon((htmlZoom) =>
-    parseInt(htmlZoom) > 30 ? parseInt(htmlZoom) - 10 + '%' : '30%',
+    `${Math.max(parseInt(htmlZoom) - 10, 30)}%`
   );
 }