move listener definitions above references

open-my-page-button/background.js

@@ -1,15 +1,16 @@
- /*
- Add openMyPage() as a listener to clicks on the browser action.
- */
- chrome.browserAction.onClicked.addListener(openMyPage);
- 
- /*
- Open a new tab, and load "my-page.html" into it.
- */
- function openMyPage() {
-   console.log("injecting");
-    chrome.tabs.create({
-      "url": chrome.extension.getURL("my-page.html")
-    }); 
- }
+/*
+Open a new tab, and load "my-page.html" into it.
+*/
+function openMyPage() {
+  console.log("injecting");
+   chrome.tabs.create({
+     "url": chrome.extension.getURL("my-page.html")
+   });
+}
+
+
+/*
+Add openMyPage() as a listener to clicks on the browser action.
+*/
+chrome.browserAction.onClicked.addListener(openMyPage);
  

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

@@ -10,13 +10,6 @@ window.addEventListener("message", function(event) {
   }
 });
 
-/*
-Add messagePageScript() as a listener to click events on
-the "from-content-script" element.
-*/
-var fromContentScript = document.getElementById("from-content-script");
-fromContentScript.addEventListener("click", messagePageScript);
-
 /*
 Send a message to the page script.
 */
@@ -26,3 +19,10 @@ function messagePageScript() {
     message: "Message from the content script"
   }, "https://mdn.github.io");
 }
+
+/*
+Add messagePageScript() as a listener to click events on
+the "from-content-script" element.
+*/
+var fromContentScript = document.getElementById("from-content-script");
+fromContentScript.addEventListener("click", messagePageScript);

user-agent-rewriter/background.js

@@ -19,16 +19,6 @@ Initialize the UA to Firefox 41.
 */
 var ua = uaStrings["Firefox 41"];
 
-/*
-Add rewriteUserAgentHeader as a listener to onBeforeSendHeaders,
-only for the target page.
-
-Make it "blocking" so we can modify the headers.
-*/
-chrome.webRequest.onBeforeSendHeaders.addListener(rewriteUserAgentHeader,
-                                          {urls: [targetPage]},
-                                          ["blocking", "requestHeaders"]);
-
 /*
 Rewrite the User-Agent header to "ua".
 */
@@ -41,6 +31,16 @@ function rewriteUserAgentHeader(e) {
   return {requestHeaders: e.requestHeaders};
 }
 
+/*
+Add rewriteUserAgentHeader as a listener to onBeforeSendHeaders,
+only for the target page.
+
+Make it "blocking" so we can modify the headers.
+*/
+chrome.webRequest.onBeforeSendHeaders.addListener(rewriteUserAgentHeader,
+                                          {urls: [targetPage]},
+                                          ["blocking", "requestHeaders"]);
+
 /*
 Update ua to a new value, mapped from the uaString parameter.
 */