Updated for review comments

export-helpers/README.md

@@ -2,27 +2,46 @@
 
 ## What it does
 
-This extension demonstrates how to use export helpers in Firefox to share
+This extension demonstrates how to use [export helpers](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Content_scripts#Sharing_content_script_objects_with_page_scripts) in Firefox to share
 JavaScript objects defined in content scripts with scripts loaded by web pages.
 
-It has a background script that does two things:
+## How it works
 
-* execute a content script in the current tab, when the user clicks a browser action
-* listen for messages from the content script, and display a notification when the message arrives.
+This example is in two parts:
+
+* an extension that consists of a content script and a background script
+* a web page at: https://mdn.github.io/webextensions-examples/export-helpers.html
+
+### The extension
+
+ The extension loads a content script into the page at: https://mdn.github.io/webextensions-examples/export-helpers.html. The content script:
  
-The content script then:
- 
- * defines a function `notify()` and exports that to the page as a property
- of the global `window` object.
+ * defines a function `notify()` and uses `exportFunction()` to export it to the page as a property of the global `window` object.
  * defines an object `messenger`, that has a member function `notify()`, and
- exports that to the page as a property of the global `window` object.
- * creates an object `messenger2` directly in the page's scope
- as a property of the global `window` object, then
- exports a function `notify()` as a member of that object.
+uses `cloneInto()` to export that to the page as a property of the global `window` object.
  
-All that means that after clicking the browser action, any scripts loaded by
-the current page will be able to do things like this:
- 
-     window.notify("Message from the page script!");
-     window.messenger.notify("Message from the page script!");
-     window.messenger2.notify("Message from the page script!");
+ In the implementation of `notify()`, the content script sends a message to the extension's background script: when the background script gets the messages, it displays a [notification](https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/notifications).
+
+## The page
+
+The page is just a normal web page. It contains two buttons and loads a script. The script:
+
+* listens for clicks on the first button and calls:
+
+
+    window.notify("Message from the page script!");
+
+* listens for clicks on the other button and calls:
+
+
+    window.messenger.notify("Message from the page script!");
+
+These items are available in the page's scope because the content script exported them.
+
+## How to us it
+
+To see the extension in action:
+
+1. install the extension
+2. visit https://mdn.github.io/webextensions-examples/export-helpers.html
+3. click one of the buttons in the page. You should see a notification from the extension.

export-helpers/background.js

@@ -1,28 +1,8 @@
-function onExecuted() {
-  if (chrome.runtime.lastError) {
-    console.log(chrome.runtime.lastError);
-  }
-}
-
-/*
-Execute content script in the active tab.
-*/
-function loadContentScript() {
-  chrome.tabs.executeScript({
-    file: "/content_scripts/export.js"
-  }, onExecuted);
-}
-
-/*
-Add loadContentScript() as a listener to clicks on the browser action.
-*/
-chrome.browserAction.onClicked.addListener(loadContentScript);
-
-/*
-Show a notification when we get messages from the content script.
-*/
-chrome.runtime.onMessage.addListener((message) => {
-  chrome.notifications.create({
+/**
+ * Show a notification when we get messages from the content script.
+ */
+browser.runtime.onMessage.addListener((message) => {
+  browser.notifications.create({
     type: "basic",
     title: "Message from the page",
     message: message.content

export-helpers/content_scripts/export.js

@@ -1,23 +1,24 @@
 
-/*
-Define a function in the content script's scope, then export it
-into the page script's scope.
-*/
+/**
+ * Define a function in the content script's scope, then export it
+ * into the page script's scope.
+ */
 function notify(message) {
-  chrome.runtime.sendMessage({content: "Function call: " + message});
+  browser.runtime.sendMessage({content: "Function call: " + message});
 }
 
 exportFunction(notify, window, {defineAs:'notify'});
-/*
-Create an object that contains functions in the content script's scope,
-then clone it into the page script's scope.
 
-Because the object contains functions, the cloneInto call must include
-the `cloneFunctions` option.
-*/
+/**
+ * Create an object that contains functions in the content script's scope,
+ * then clone it into the page script's scope.
+ *
+ * Because the object contains functions, the cloneInto call must include
+ * the `cloneFunctions` option.
+ */
 var messenger = {
   notify: function(message) {
-    chrome.runtime.sendMessage({content: "Object method call 1: " + message});
+    browser.runtime.sendMessage({content: "Object method call: " + message});
   }
 };
 

export-helpers/manifest.json

@@ -20,9 +20,12 @@
     "scripts": ["background.js"]
   },
 
-  "browser_action": {
-    "default_icon": "icons/arrow.svg"
-  },
+  "content_scripts": [
+    {
+      "matches": ["<all_urls>"],
+      "js": ["content_scripts/export.js"]
+    }
+  ],
   
   "permissions": [
     "activeTab",