diff --git a/frontend_tests/node_tests/alert_words.js b/frontend_tests/node_tests/alert_words.js
index 6f841e978a..c9c66ed73c 100644
--- a/frontend_tests/node_tests/alert_words.js
+++ b/frontend_tests/node_tests/alert_words.js
@@ -18,29 +18,29 @@ global.people.add({
 global.people.initialize_current_user(42);
 
 
-var regular_message = { sender_email: 'another@zulip.com', content: '<p>a message</p>'};
-var own_message = { sender_email: 'tester@zulip.com', content: '<p>hey this message alertone</p>',
+const regular_message = { sender_email: 'another@zulip.com', content: '<p>a message</p>'};
+const own_message = { sender_email: 'tester@zulip.com', content: '<p>hey this message alertone</p>',
                     alerted: true };
-var other_message = { sender_email: 'another@zulip.com', content: '<p>another alertone message</p>',
+const other_message = { sender_email: 'another@zulip.com', content: '<p>another alertone message</p>',
                       alerted: true };
-var caps_message = { sender_email: 'another@zulip.com', content: '<p>another ALERTtwo message</p>',
+const caps_message = { sender_email: 'another@zulip.com', content: '<p>another ALERTtwo message</p>',
                      alerted: true };
-var alertwordboundary_message = { sender_email: 'another@zulip.com',
+const alertwordboundary_message = { sender_email: 'another@zulip.com',
                                   content: '<p>another alertthreemessage</p>', alerted: false };
-var multialert_message = { sender_email: 'another@zulip.com', content:
+const multialert_message = { sender_email: 'another@zulip.com', content:
                            '<p>another alertthreemessage alertone and then alerttwo</p>',
                            alerted: true };
-var unsafe_word_message = { sender_email: 'another@zulip.com', content: '<p>gotta al*rt.*s all</p>',
+const unsafe_word_message = { sender_email: 'another@zulip.com', content: '<p>gotta al*rt.*s all</p>',
                             alerted: true };
-var alert_in_url_message = { sender_email: 'another@zulip.com', content: '<p>http://www.google.com/alertone/me</p>',
+const alert_in_url_message = { sender_email: 'another@zulip.com', content: '<p>http://www.google.com/alertone/me</p>',
                             alerted: true };
-var question_word_message = { sender_email: 'another@zulip.com', content: '<p>still alertone? me</p>',
+const question_word_message = { sender_email: 'another@zulip.com', content: '<p>still alertone? me</p>',
                             alerted: true };
 
-var alert_domain_message = { sender_email: 'another@zulip.com', content: '<p>now with link <a href="http://www.alerttwo.us/foo/bar" target="_blank" title="http://www.alerttwo.us/foo/bar">www.alerttwo.us/foo/bar</a></p>',
+const alert_domain_message = { sender_email: 'another@zulip.com', content: '<p>now with link <a href="http://www.alerttwo.us/foo/bar" target="_blank" title="http://www.alerttwo.us/foo/bar">www.alerttwo.us/foo/bar</a></p>',
                      alerted: true };
 // This test ensure we are not mucking up rendered HTML content.
-var message_with_emoji = { sender_email: 'another@zulip.com', content: '<p>I <img alt=":heart:" class="emoji" src="/static/generated/emoji/images/emoji/unicode/2764.png" title="heart"> emoji!</p>',
+const message_with_emoji = { sender_email: 'another@zulip.com', content: '<p>I <img alt=":heart:" class="emoji" src="/static/generated/emoji/images/emoji/unicode/2764.png" title="heart"> emoji!</p>',
                            alerted: true };
 
 (function test_notifications() {
@@ -56,7 +56,7 @@ var message_with_emoji = { sender_email: 'another@zulip.com', content: '<p>I <im
 }());
 
 (function test_munging() {
-    var saved_content = regular_message.content;
+    let saved_content = regular_message.content;
     alert_words.process_message(regular_message);
     assert.equal(saved_content, regular_message.content);
 
@@ -82,8 +82,8 @@ var message_with_emoji = { sender_email: 'another@zulip.com', content: '<p>I <im
     assert.equal(question_word_message.content, "<p>still <span class='alert-word'>alertone</span>? me</p>");
 
     alert_words.process_message(alert_domain_message);
-    assert.equal(alert_domain_message.content, '<p>now with link <a href="http://www.alerttwo.us/foo/bar" target="_blank" title="http://www.alerttwo.us/foo/bar">www.<span class=\'alert-word\'>alerttwo</span>.us/foo/bar</a></p>');
+    assert.equal(alert_domain_message.content, `<p>now with link <a href="http://www.alerttwo.us/foo/bar" target="_blank" title="http://www.alerttwo.us/foo/bar">www.<span class='alert-word'>alerttwo</span>.us/foo/bar</a></p>`);
 
     alert_words.process_message(message_with_emoji);
-    assert.equal(message_with_emoji.content, '<p>I <img alt=":heart:" class="emoji" src="/static/generated/emoji/images/emoji/unicode/2764.png" title="heart"> <span class=\'alert-word\'>emoji</span>!</p>');
+    assert.equal(message_with_emoji.content, `<p>I <img alt=":heart:" class="emoji" src="/static/generated/emoji/images/emoji/unicode/2764.png" title="heart"> <span class='alert-word'>emoji</span>!</p>`);
 }());