diff --git a/frontend_tests/node_tests/widgetize.js b/frontend_tests/node_tests/widgetize.js
index b8bf6fe008..fcc7bb603a 100644
--- a/frontend_tests/node_tests/widgetize.js
+++ b/frontend_tests/node_tests/widgetize.js
@@ -96,14 +96,14 @@ run_test('activate', () => {
     is_widget_elem_inserted = false;
     is_widget_activated = false;
     is_event_handled = false;
-    assert.equal(widgetize.widget_contents[opts.message.id], undefined);
+    assert(!widgetize.widget_contents.has(opts.message.id));
 
     widgetize.activate(opts);
 
     assert(is_widget_elem_inserted);
     assert(is_widget_activated);
     assert(is_event_handled);
-    assert.equal(widgetize.widget_contents[opts.message.id], widget_elem);
+    assert.equal(widgetize.widget_contents.get(opts.message.id), widget_elem);
 
     is_widget_elem_inserted = false;
     is_widget_activated = false;
diff --git a/static/js/widgetize.js b/static/js/widgetize.js
index 09c8ef436a..637ed4fc0e 100644
--- a/static/js/widgetize.js
+++ b/static/js/widgetize.js
@@ -5,7 +5,7 @@ const widgets = new Map([
     ["zform", zform],
 ]);
 
-const widget_contents = {};
+const widget_contents = new Map();
 exports.widget_contents = widget_contents;
 
 function set_widget_in_message(row, widget_elem) {
@@ -41,7 +41,7 @@ exports.activate = function (in_opts) {
         return;
     }
 
-    let widget_elem = widget_contents[message.id];
+    let widget_elem = widget_contents.get(message.id);
     if (widget_elem) {
         set_widget_in_message(row, widget_elem);
         return;
@@ -58,7 +58,7 @@ exports.activate = function (in_opts) {
         extra_data: extra_data,
     });
 
-    widget_contents[message.id] = widget_elem;
+    widget_contents.set(message.id, widget_elem);
     set_widget_in_message(row, widget_elem);
 
     // Replay any events that already happened.  (This is common
@@ -70,16 +70,16 @@ exports.activate = function (in_opts) {
 };
 
 exports.set_widgets_for_list = function () {
-    _.each(widget_contents, function (widget_elem, idx) {
+    for (const [idx, widget_elem] of widget_contents) {
         if (current_msg_list.get(idx) !== undefined) {
             const row = current_msg_list.get_row(idx);
             set_widget_in_message(row, widget_elem);
         }
-    });
+    }
 };
 
 exports.handle_event = function (widget_event) {
-    const widget_elem = widget_contents[widget_event.message_id];
+    const widget_elem = widget_contents.get(widget_event.message_id);
 
     if (!widget_elem) {
         // It is common for submessage events to arrive on