2-way messaging

page-to-extension-messaging/content-script.js

@@ -0,0 +1,18 @@
+window.addEventListener("message", function(event) {
+  if (event.source == window &&
+      event.data.direction &&
+      event.data.direction == "from-page-script") {
+    alert("Content script received message: \"" + event.data.message + "\"");
+  }
+});
+
+var fromContentScript = document.getElementById("from-content-script");
+
+fromContentScript.addEventListener("click", messagePageScript);
+
+function messagePageScript() {
+  window.postMessage({
+    direction: "from-content-script",
+    message: "Message from the content script"
+  }, "*");
+}