diff --git a/packages/hydrooj/src/entry/worker.ts b/packages/hydrooj/src/entry/worker.ts
index a36a02b4..0bc2d8f9 100644
--- a/packages/hydrooj/src/entry/worker.ts
+++ b/packages/hydrooj/src/entry/worker.ts
@@ -7,7 +7,6 @@ import fs from 'fs-extra';
 import { Context } from '../context';
 import { Logger } from '../logger';
 import db from '../service/db';
-import { sleep } from '../utils';
 import {
     addon, builtinModel, handler, lib, locale, model,
     script, service, setting, template,
diff --git a/packages/hydrooj/src/handler/import.ts b/packages/hydrooj/src/handler/import.ts
index 945b5ade..ac74f687 100644
--- a/packages/hydrooj/src/handler/import.ts
+++ b/packages/hydrooj/src/handler/import.ts
@@ -50,13 +50,15 @@ class ProblemImportHydroHandler extends Handler {
             });
         });
         try {
-            const problems = await fs.readdir(tmpdir);
-            for (const i of problems) {
+            const problems = await fs.readdir(tmpdir, { withFileTypes: true });
+            for (const { name: i, isDirectory } of problems) {
+                if (!isDirectory()) continue;
                 const files = await fs.readdir(path.join(tmpdir, i));
                 if (!files.includes('problem.yaml')) continue;
                 const content = fs.readFileSync(path.join(tmpdir, i, 'problem.yaml'), 'utf-8');
                 const pdoc: ProblemDoc = yaml.load(content) as any;
-                let pid = pdoc?.pid;
+                if (!pdoc) continue;
+                let pid = pdoc.pid;
                 if (pid) {
                     const current = await problem.get(domainId, pid);
                     if (current) pid = undefined;
diff --git a/packages/ui-default/components/datepicker/timepicker.ts b/packages/ui-default/components/datepicker/timepicker.ts
index 582a8a7e..3271b3eb 100644
--- a/packages/ui-default/components/datepicker/timepicker.ts
+++ b/packages/ui-default/components/datepicker/timepicker.ts
@@ -186,7 +186,7 @@ export default class TimePicker {
   }; // TimePicker.prototype.scope
 
   parse(type, value, options) {
-    let hour; let minutes; let isPM; let item; let parseValue;
+    let hour; let minutes; let item; let parseValue;
     const clock = this;
     const parsingObject = {};
     if (!value || typeof value !== 'string') return value;
@@ -219,7 +219,7 @@ export default class TimePicker {
     }
 
     // Calculate it in minutes and return.
-    return (isPM ? hour + 12 : hour) * MINUTES_IN_HOUR + minutes;
+    return hour * MINUTES_IN_HOUR + minutes;
   }
 
   nodes(isOpen) {
diff --git a/packages/ui-default/components/message/index.page.ts b/packages/ui-default/components/message/index.page.ts
index 222b477c..f59e77d5 100644
--- a/packages/ui-default/components/message/index.page.ts
+++ b/packages/ui-default/components/message/index.page.ts
@@ -100,7 +100,7 @@ const messagePage = new AutoloadPage('messagePage', (pagename) => {
     localStorage.setItem('pages', JSON.stringify(c.filter((i) => i !== selfId)));
     if (!isMaster) return;
     localStorage.removeItem('page.master');
-    channel?.postMessage({ type: 'master' });
+    channel.postMessage({ type: 'master' });
   };
 
   function asMaster() {
diff --git a/packages/ui-default/polyfill.ts b/packages/ui-default/polyfill.ts
index ce083f44..202215e4 100644
--- a/packages/ui-default/polyfill.ts
+++ b/packages/ui-default/polyfill.ts
@@ -63,6 +63,7 @@ if (!(window.matchMedia('all').addListener || window.matchMedia('all').addEventL
         for (let i = 0, il = listeners.length; i < il; i++) {
           if (listeners[i] === listener) {
             listeners.splice(i, 1);
+            i--;
           }
         }
       };
diff --git a/packages/vjudge/src/providers/uoj.ts b/packages/vjudge/src/providers/uoj.ts
index 549d21ed..74846e37 100644
--- a/packages/vjudge/src/providers/uoj.ts
+++ b/packages/vjudge/src/providers/uoj.ts
@@ -55,7 +55,7 @@ export default class UOJProvider implements IBasicProvider {
             this.cookie = header['set-cookie'];
         }
         let value = /_token *: *"(.+?)"/g.exec(html);
-        if (value) return value?.[1];
+        if (value) return value[1];
         value = /_token" value="(.+?)"/g.exec(html);
         return value?.[1];
     }