diff --git a/lib/app.js b/lib/app.js
index 0d1c939..21a39dc 100644
--- a/lib/app.js
+++ b/lib/app.js
@@ -1,15 +1,12 @@
 $(document).ready(function () {
-    // seq: シーケンス番号
-    $.each(["new_version", "old_version"], function () {
-        $("input[name='" + this + "']").each(function (idx, elem) {
-            if (idx == 0) {
-                $(elem).attr('checked', 'checked');
-            }
-            $(elem).attr('seq', idx);
-        });
+    var $new_versions = $("input[name='new_version']");
+    var $old_versions = $("input[name='old_version']");
+    $new_versions.first().attr('checked', 'checked');
+    $old_versions.first().attr('checked', 'checked');
+    $new_versions.each(function (index) {
+        $(this).data('pair', $old_versions.eq(index));
     });
-    $("input[name='new_version']").change(function () {
-        var seq = parseInt($(this).attr('seq'));
-        $("input[name='old_version']").eq(seq).attr('checked', 'checked');
+    $new_versions.change(function () {
+        $(this).data('pair').attr('checked', 'checked');
     });
 });
\ No newline at end of file