Chrome extension sendMessage

Question

I want my content script, simply to show a pageIcon if there is a textarea on the page.

My content.js (using jquery) does this:

$('textarea').each(function() {
    chrome.extension.sendMessage({greeting: "hello"}, function(response) {
       console.log(response);
    });
});

Then my background.js has this:

chrome.extension.onMessage.addListener(

    function(request, sender, sendResponse) {
        chrome.pageAction.show(sender.tab.id);
    } 
});

Which should be incredibly simple. If there's a textarea, show the icon.

I have tried all kinds of variations from sample code and nothing works. All I ever get is:

Port error: Could not establish connection. Receiving end does not exist.

in the console.

Any ideas where I'm going wrong?

The documentation for Chrome extensions is generally excellent. You did not properly read the documentation: Event listeners to [`chrome.extension.onmessage`](http://code.google.com/chrome/extensions/extension.html#event-onMessage) receive only one parameter: The object containing `request`, `sender`, `sendResponse`. (since Chrome 20, [`onRequest` and `sendRequest` have been replaced with `onMessage` and `sendMessage`](http://stackoverflow.com/a/11412113)). This is probably not the cause of the error though. Are you sure that the `onMessage` event listener is attached (ie no error occurred)? — Rob W, Jul 17 '12 at 21:35
Change onMessage to onRequest and try again, if error persists then you have to look at console log of background script (in Extensions -> Inspect Views: *** there should be your script, jusc lick and go to console, look at error message) — Aleksandar Toplek, Jul 18 '12 at 11:30

score 7 · Accepted Answer · answered Aug 17 '12 at 18:41

7

I think you have an extra curly bracket in the background script.

chrome.extension.onMessage.addListener(

    function(request, sender, sendResponse) {
        chrome.pageAction.show(sender.tab.id);
    } 
});

should be

chrome.extension.onMessage.addListener(

    function(request, sender, sendResponse) {
        chrome.pageAction.show(sender.tab.id);
    } 
);

answered Aug 17 '12 at 18:41

ron

I'm calling sendResponse(from extension) back to send some content but not getting called.Please help. – pavan Sep 24 '14 at 14:33

1 Answers1