Access window object from a background Chrome extension

Question

I want to access the properties of a window object from a background script. I have this in manifest.json:

{
    "..": "..",
    "permissions": ["http://*.mysite.net/"],
    "background": {
        "scripts": ["extension.js"]
    }
}

and this in extension.js:

chrome.tabs.onUpdated.addListener(function (tabId, changeInfo, tab) {
    if (changeInfo.status === 'complete') {

        var tabWindowObject = ??

        setInterval(tabWindowObject.someFunction, 10);
    }
});

I need it here, not in another place (no content scripts and no script injection). How do I get the tabWindowObject in extension.js? In other words, I want to access the context of a tab inside a background script Chrome extension.

You can't. If it's an object defined by the webpage code, then you can only access it through script injection from a content script. — rsanchez
– rsanchez, Commented Mar 21, 2014 at 23:48

Jeffrey Yasskin · Accepted Answer · 2014-03-24 02:00:20Z

13

You can't. The extension's background page runs in one process, while the tab that was updated runs in a separate process. Different processes can't share objects, so you can't directly access the window object of a tab from an extension's background page. You have to use a content script to get extension code to run inside the tab's process.

answered Mar 24, 2014 at 2:00

Jeffrey Yasskin

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2 Comments

f.ardelian Over a year ago

And then I have to inject code using <script> tags to pass messages from the web page to the content script and from the content script to the background script. I figured it out after a lot of searching, so I'm just adding to your answer. There's no way to access objects, but I can send JSON data (which is serialized into strings when passed to message listeners).

Jeffrey Yasskin Over a year ago

You may be able to avoid the <script> tags, depending on exactly what you need to do: the web page can fire events on DOM objects, and the content script can listen to those.

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