diff --git a/views/contest_edit.ejs b/views/contest_edit.ejs
index d82fda3..e4fe124 100644
--- a/views/contest_edit.ejs
+++ b/views/contest_edit.ejs
@@ -85,7 +85,7 @@ $(function () {
         onResponse: function (response) {
           var a = $('#search_admins').val().map(function (x) { return parseInt(x) });
           if (response.results) {
-            response.results = response.results.filter(x => !a.includes(parseInt(x.value)));
+            response.results = response.results.filter(function(x){ return !a.includes(parseInt(x.value))});
           }
           return response;
         },
@@ -100,7 +100,7 @@ $(function () {
         onResponse: function (response) {
           var a = $('#search_problems').val().map(function (x) { return parseInt(x) });
           if (response.results) {
-            response.results = response.results.filter(x => !a.includes(parseInt(x.value)));
+            response.results = response.results.filter(function(x) {return !a.includes(parseInt(x.value));});
           }
           return response;
         },
diff --git a/views/problem_data.ejs b/views/problem_data.ejs
index ac2969a..63e2c96 100644
--- a/views/problem_data.ejs
+++ b/views/problem_data.ejs
@@ -145,7 +145,7 @@ function getIcon(filename) {
         </div>
         <script>
         function check_replace() {
-          var old_files = <%- JSON.stringify((testdata && testdata.files ? testdata.files : []).map(x => x.filename)) %>;
+          var old_files = <%- JSON.stringify((testdata && testdata.files ? testdata.files : []).map(function(x) { return x.filename; })) %>;
           var replaced_files = Array.prototype.slice.call($('#upload_file')[0].files).map(function (x) { return x.name; }).filter(function (x) { return old_files.includes(x); });
           var s = '';
           for (let file of replaced_files) s += '<samp>' + file + '</samp><br>';
diff --git a/views/problem_edit.ejs b/views/problem_edit.ejs
index 90608a1..ec0dd9c 100644
--- a/views/problem_edit.ejs
+++ b/views/problem_edit.ejs
@@ -98,7 +98,7 @@ $(function () {
         onResponse: function (response) {
           var a = $('#search_tags').val().map(function (x) { return parseInt(x) });
           if (response.results) {
-            response.results = response.results.filter(x => !a.includes(parseInt(x.value)));
+            response.results = response.results.filter(function(x) { return !a.includes(parseInt(x.value));});
           }
           return response;
         },
diff --git a/views/submission.ejs b/views/submission.ejs
index bdb7a90..a870138 100644
--- a/views/submission.ejs
+++ b/views/submission.ejs
@@ -173,19 +173,20 @@ const vueApp = new Vue({
       return statusToString[statusCode];
     },
     firstNonAC(t) {
-      if (t.every(v => v === TestcaseResultType.Accepted)) {
+      if (t.every(function(v){ return v === TestcaseResultType.Accepted;})) {
         return TestcaseResultType.Accepted;
       } else {
-        return t.find(r => r !== TestcaseResultType.Accepted);
+        return t.find(function(r) { return r !== TestcaseResultType.Accepted;});
       }
     },
     getSubtaskResult(t) {
-      if (t.cases.some(c => c.status === TaskStatus.Running)) {
+      if (t.cases.some(function(c){ return c.status === TaskStatus.Running;})) {
         return "Running";
-      } else if (t.cases.some(c => c.status === TaskStatus.Waiting)) {
+      } else if (t.cases.some(function(c) { return c.status === TaskStatus.Waiting;})) {
         return "Waiting";
-      } else if (t.cases.every(c => c.status === TaskStatus.Done || c.status === TaskStatus.Skipped)) {
-        return this.getStatusString(this.firstNonAC(t.cases.filter(c => c.result).map(c => c.result.type)));
+      } else if (t.cases.every(function(c){ return c.status === TaskStatus.Done || c.status === TaskStatus.Skipped;})) {
+        return this.getStatusString(this.firstNonAC(t.cases.filter(function(c) { return c.result; })
+          .map(function(c) { return c.result.type;})));
       } else {
         return "System Error";
       }
@@ -208,7 +209,7 @@ const vueApp = new Vue({
     }
   },
   mounted() {
-    $(document).ready(() => $('.ui.accordion').accordion());
+    $(document).ready(function(){ $('.ui.accordion').accordion()});
   },
   updated() {
     $('.ui.accordion').accordion("refresh");
@@ -218,13 +219,13 @@ if (token != null) {
   const loadSocketIO = function () {
     let currentVersion = 0;
     const socket = io(socketUrl);
-    socket.on('connect', () => {
-      socket.on('start', () => {
+    socket.on('connect', function () {
+      socket.on('start', function () {
         vueApp.roughData.running = true;
         console.log("Judge start!");
         vueApp.detailResult = {};
       });
-      socket.on('update', (p) => {
+      socket.on('update', function (p) {
         console.log("Delta: " + JSON.stringify(p));
         if (p.from === currentVersion) {
           currentVersion = p.to;
@@ -234,14 +235,14 @@ if (token != null) {
           setTimeout(loadSocketIO, 0);
         }
       });
-      socket.on('finish', (p) => {
+      socket.on('finish', function (p) {
         console.log("Judge finished");
         vueApp.roughData.running = false;
         vueApp.roughData.result = p.roughResult;
         vueApp.detailResult = p.result;
         socket.close();
       });
-      socket.emit('join', token, (data) => {
+      socket.emit('join', token, function (data) {
         console.log("join! " + JSON.stringify(data));
         if (data && data.ok) {
           if (data.finished) {
diff --git a/views/submissions.ejs b/views/submissions.ejs
index a6b144f..67626b9 100644
--- a/views/submissions.ejs
+++ b/views/submissions.ejs
@@ -124,24 +124,24 @@ const vueApp = new Vue({
   },
 });
 
-if (itemList.some(t => t.token != null)) {
+if (itemList.some(function(t) {return t.token != null;})) {
   const socket = io(socketUrl);
-  socket.on('connect', () => {
-    for (let x of itemList.filter(x => x.token != null)){
-      const getItem = (id) => itemList.find(x => x.info.taskId === id);
-      socket.on('start', (data) => {
+  socket.on('connect', function () {
+    for (let x of itemList.filter(function(x) {return x.token != null;})){
+      const getItem = function (id){ return itemList.find(function(x){ return x.info.taskId === id; })};
+      socket.on('start', function (data) {
         getItem(data.taskId).running = true;
       });
 
-      socket.on('finish', (data) => {
+      socket.on('finish', function (data) {
         getItem(data.taskId).running = false;
         getItem(data.taskId).result = data.result;
-        if (itemList.every(x => x.result)) {
+        if (itemList.every(function(x){ return x.result; })) {
           socket.close();
         }
       });
 
-      socket.emit('join', x.token, (data) => {
+      socket.emit('join', x.token, function (data) {
         if (data && data.ok) {
           if (data.running) {
             x.running = true;