Can a Chrome extension monitor XHR events (or other events) from the page it's running against?

I'm building a Chrome extension that manipulates the content of the page, but the content I'm interested in only shows up when the user has clicked a button and the data has then been loaded from an Ajax call.

At the moment the ex开发者_StackOverflow社区tension monitors the page with a SetTimeout but it's clumsy.

Can an extension know when an Ajax call has been initiated, and when it ended? or can the extension somehow receive events from the page?

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I don't know an easy way to monitor XHR requests, but you can monitor any changes being made to a page structure by listening to DOMSubtreeModified event. So when ajax call is done and elements are added/removed/changed on a page - you will be notified.

document.addEventListener("DOMSubtreeModified", function(event){
        //something has changed
});