eslint: Fix no-implicit-coercion.

https://eslint.org/docs/rules/no-implicit-coercion

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

.eslintrc.json

@@ -54,6 +54,7 @@
         "no-else-return": "error",
         "no-eq-null": "error",
         "no-eval": "error",
+        "no-implicit-coercion": "error",
         "no-implied-eval": "error",
         "no-inner-declarations": "off",
         "no-iterator": "error",

frontend_tests/node_tests/drafts.js

@@ -145,7 +145,7 @@ run_test("snapshot_message", () => {
             return draft.type;
         };
         global.compose_state.composing = function () {
-            return !!draft.type;
+            return Boolean(draft.type);
         };
         global.compose_state.message_content = function () {
             return draft.content;

static/js/compose_state.js

@@ -13,7 +13,7 @@ exports.get_message_type = function () {
 exports.composing = function () {
     // This is very similar to get_message_type(), but it returns
     // a boolean.
-    return !!message_type;
+    return Boolean(message_type);
 };
 
 exports.focus_in_empty_compose = function () {

static/js/lightbox.js

@@ -201,9 +201,9 @@ exports.parse_image_data = function (image) {
 
     // if wrapped in the .youtube-video class, it will be length = 1, and therefore
     // cast to true.
-    const is_youtube_video = !!$image.closest(".youtube-video").length;
+    const is_youtube_video = Boolean($image.closest(".youtube-video").length);
-    const is_vimeo_video = !!$image.closest(".vimeo-video").length;
+    const is_vimeo_video = Boolean($image.closest(".vimeo-video").length);
-    const is_embed_video = !!$image.closest(".embed-video").length;
+    const is_embed_video = Boolean($image.closest(".embed-video").length);
 
     // check if image is descendent of #preview_content
     const is_compose_preview_image = $image.closest("#preview_content").length === 1;

static/js/notifications.js

@@ -163,7 +163,7 @@ exports.redraw_title = function () {
             // Make sure we're working with a number, as a defensive programming
             // measure.  And we don't have images above 99, so display those as
             // 'infinite'.
-            n = +new_message_count;
+            n = Number(new_message_count);
             if (n > 99) {
                 n = "infinite";
             }

static/js/overlays.js

@@ -11,7 +11,7 @@ function reset_state() {
 }
 
 exports.is_active = function () {
-    return !!open_overlay_name;
+    return Boolean(open_overlay_name);
 };
 
 exports.is_modal_open = function () {

static/js/recent_topics.js

@@ -175,7 +175,7 @@ function format_topic(topic_data) {
     // We only supply the data to the topic rows and let jquery
     // display / hide them according to filters instead of
     // doing complete re-render.
-    const topic_muted = !!muting.is_topic_muted(stream_id, topic);
+    const topic_muted = Boolean(muting.is_topic_muted(stream_id, topic));
     const stream_muted = stream_data.is_muted(stream_id);
     const muted = topic_muted || stream_muted;
     const unread_count = unread.unread_topic_counter.get(stream_id, topic);
@@ -266,7 +266,7 @@ exports.filters_should_hide_topic = function (topic_data) {
     }
 
     if (!filters.has("include_muted")) {
-        const topic_muted = !!muting.is_topic_muted(msg.stream_id, msg.topic);
+        const topic_muted = Boolean(muting.is_topic_muted(msg.stream_id, msg.topic));
         const stream_muted = stream_data.is_muted(msg.stream_id);
         if (topic_muted || stream_muted) {
             return true;

static/js/settings_org.js

@@ -733,7 +733,7 @@ exports.build_page = function () {
                     $("#id_realm_message_content_edit_limit_minutes"),
                 );
                 // Disable editing if the parsed time limit is 0 seconds
-                data.allow_message_editing = !!data.message_content_edit_limit_seconds;
+                data.allow_message_editing = Boolean(data.message_content_edit_limit_seconds);
             } else {
                 data.allow_message_editing = true;
                 data.message_content_edit_limit_seconds = settings_config.msg_edit_limit_dropdown_values.get(
@@ -748,7 +748,7 @@ exports.build_page = function () {
                     $("#id_realm_message_content_delete_limit_minutes"),
                 );
                 // Disable deleting if the parsed time limit is 0 seconds
-                data.allow_message_deleting = !!data.message_content_delete_limit_seconds;
+                data.allow_message_deleting = Boolean(data.message_content_delete_limit_seconds);
             } else {
                 data.allow_message_deleting = true;
                 data.message_content_delete_limit_seconds = settings_config.msg_delete_limit_dropdown_values.get(