How to grab content from DOM of page and output to extension's popup?

[birdofprey]

I'm trying to grab data from the webpage's DOM, and output it into the
extension popup, but none of the JS in popup.html seems to have any
effect on the DOM of popup.html.

For example, in this example of popup.html below, I'm using
content_script.js to grab content from the webpage's DOM, and output
it into the extension popup.

<!--Start-->
<div id="extensioncontent"></div>
<a onclick="click()">Scrape</a>

<script>
function click() {
chrome.tabs.executeScript(null, {file: "content_script.js"});
document.getElementById("extensioncontent").innerHTML =
stringDefinedInContentScript;
window.close();
}
</script>
<!--End-->

I tried using the example here:
http://code.google.com/chrome/extensions/messaging.html
in content_script.js, but I'm not sure what greeting: "hello" and
response should be.

contentscript.js
================
chrome.extension.sendRequest({greeting: "hello"}, function(response) {
console.log(response.farewell);
});

[Arne Roomann-Kurrik]

You can't access data in a content script directly from a popup.  You had the right idea with messaging, but it looks like your popup wasn't set up to listen for messages.  To do this, you'd need to do something like this:

  chrome.extension.onRequest.addListener(
      function(request, sender, sendResponse) {
          if (request.message) {

              // Do something with the text

          }

          sendResponse({});

      }

  );

Then your content script should have code similar to:

    var myMessage = "...";  // Assign your text to this variable

    chrome.extension.sendRequest({message: myMessage}, function(response) {});

~Arne

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[birdofprey]

Hmm, it's still not making any changes to the popup, even after
assigning a value to myMessage and passing that variable.

Here's what I have:

===============
content_script.js
===============
var myMessage =
document.getElementById("topfoot").getElementsByTagName("small")
[0].innerHTML;

chrome.extension.sendRequest({message: myMessage}, function(response)
{});

===============
popup.html
===============
<style type="text/css">
a {text-decoration:underline;}
</style>

<div id="quoted">Placeholder</div>

<a onclick="click()">Scrape</a>

<script type="text/javascript">

function click() {
chrome.tabs.executeScript(null, {file: "content_script.js"});

document.getElementById("quoted").innerHTML = myMessage;
window.close();
}

chrome.extension.onRequest.addListener(
function(request, sender, sendResponse) {
if (request.message) {

document.getElementById("quoted").innerHTML =
myMessage;
}
sendResponse({});
}
);
</script>

===============
manifest.json
===============
{
"name": "A browser action with a popup that grabs a quote.",
"version": "1.0",
"permissions": [
"tabs", "http://*/*", "https://*/*"
],
"browser_action": {
"default_title": "Grab a quote.",
"default_icon": "icon.png",
"popup": "popup.html"
}
}

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[birdofprey]

(This is when using slashdot.org as an example page.)

[Arne Roomann-Kurrik]

Try changing the code from:

if (request.message) {
    document.getElementById("quoted").innerHTML = myMessage;
}

to 

if (request.message) {
    document.getElementById("quoted").innerHTML = request.message;
}

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[birdofprey]

That worked, thanks!

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