Setup a simple message passing via JS between content and background

extension/manifest.json

@@ -21,5 +21,5 @@
     "scripts": ["background.js"],
     "persistent": true
   },
-  "permissions": ["tabs", "storage"]
+  "permissions": ["activeTab", "tabs", "storage"]
 }

src/background.js

@@ -4,4 +4,12 @@ function main() {
   Background.main();
 }
 
+browser.browserAction.onClicked.addListener(async (tab) => {
+  try {
+    browser.tabs.sendMessage(tab.id, "Message from JS background");
+  } catch (error) {
+    error(error);
+  }
+});
+
 main();

src/content.js

@@ -4,4 +4,8 @@ function main() {
     Content.main();
 }
 
+browser.runtime.onMessage.addListener(async message => {
+    console.log("[message received]", message);
+});
+
 main();