frontend_tests: Use named functions to mock constructors.

This will stop ESLint from replacing them with arrow functions, which
cannot be constructors.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

frontend_tests/node_tests/list_render.js

@@ -6,9 +6,10 @@ zrequire('list_render');
 // that are either jQuery, Element, or just raw HTML
 // strings.  We initially test with raw strings.
 set_global('jQuery', 'stub');
-set_global('Element', function () {
+function Element() {
     return { };
-});
+}
+set_global('Element', Element);
 
 // We only need very simple jQuery wrappers for when the
 // "real" code wraps html or sets up click handlers.

frontend_tests/node_tests/markdown.js

@@ -44,9 +44,10 @@ set_global('page_params', {
     translate_emoticons: false,
 });
 
-set_global('Image', function () {
+function Image() {
     return {};
-});
+}
+set_global('Image', Image);
 emoji.initialize();
 
 const doc = "";

frontend_tests/node_tests/message_fetch.js

@@ -5,7 +5,10 @@ zrequire('message_fetch');
 
 const noop = () => {};
 
-set_global('MessageListView', function () { return {}; });
+function MessageListView() {
+    return {};
+}
+set_global('MessageListView', MessageListView);
 
 zrequire('FetchStatus', 'js/fetch_status');
 zrequire('Filter', 'js/filter');

frontend_tests/node_tests/popovers.js

@@ -42,9 +42,10 @@ set_global('stream_popover', {
 
 set_global('stream_data', {});
 
-set_global('ClipboardJS', function (sel) {
+function ClipboardJS(sel) {
     assert.equal(sel, '.copy_link');
-});
+}
+set_global('ClipboardJS', ClipboardJS);
 
 const alice = {
     email: 'alice@example.com',
@@ -95,9 +96,7 @@ function make_image_stubber() {
         return image;
     }
 
-    set_global('Image', function () {
+    set_global('Image', stub_image);
-        return stub_image();
-    });
 
     return {
         get: (i) => images[i],

frontend_tests/node_tests/presence.js

@@ -7,7 +7,10 @@ set_global('server_events', {});
 set_global('reload_state', {
     is_in_progress: return_false,
 });
-set_global('XDate', function (ms) { return {seconds: ms}; });
+function XDate(ms) {
+    return {seconds: ms};
+}
+set_global('XDate', XDate);
 
 const OFFLINE_THRESHOLD_SECS = 140;
 

frontend_tests/node_tests/settings_bots.js

@@ -24,9 +24,10 @@ zrequire('bot_data');
 zrequire('settings_bots');
 zrequire('people');
 
-set_global('ClipboardJS', function (sel) {
+function ClipboardJS(sel) {
     assert.equal(sel, '#copy_zuliprc');
-});
+}
+set_global('ClipboardJS', ClipboardJS);
 
 bot_data.initialize(bot_data_params);