Browser extension resources

I recently put together a chrome extension for a customer who wanted to detect predefined expressions in webpages. Given the size of the targetted web pages, he was concerned about performance and did not want the web site / browser to be slowed down by the extra processing involved. I designed a triple blade razor contentScript based on two web APIs which can help with the job: Blade1: to deal with any web page including the dynamic ones, I configured a mutationObserver to detect the newly created DOM elements. By the way, I'm only interested by the elements which contain text nodes (i.e. nodeType===Node.TEXT_NODE).. Blade2/ to spend CPU time on useful things, I configured an intersectionObserver to which I passed those elements. This observer detects the nodes becoming visible and feeds those to the third blade. Blade3/ finally, a simple job scheduler scans its pipeline every 5 ms and communicates with the background script which holds the content processing engine (in

I'm particularly interested in code coverage assessment in two situations: - who has never refactored a functional extension to cope for growth and new features ? When I refactor, I do variable renaming, object restructuring, code cleaning etc .., and I become very concerned about regression issues. Changes can be spread,major and devastating. So, I need to validate 100% of them. - having deployed tens of extensions, I very often start new projects from existing ones and carry over code I may not need at the end. Code coverage highlights very quickly candidate files and lines to prune off. Since 59, chrome offers a very interesting code coverage feature available thru the devtools - of course -.  Content script and background scripts (in fact all scripts!) can be studied for coverage. So open the devtools, open the console and click the "coverage" tab: - a "content scripts" checkbox next to the URL filter allows to include content scripts in the cove

Usecase I've recently come across a specific requirement from a customer who wanted a chrome extension  fiddling with the user machine file system. To be more specific, the addon was supposed to allow for the download of a cloud-based compressed file, decompress it and place the result in a specific directory for consumption by another application. As many know, filesystem is sandboxed by chrome for security reasons and it is impossible per design to write files on the user machine outside of the control of the user. I ended-up with a specific architecture outsourcing of the unauthorized job to a native app which bears none of the constraints a chrome extension does. An elegant architecture NativeMessaging Chrome API allows an extension to control - ie launch,communicate with and close - an external application: Native application can be written in any language An instance of the native app is launched when the extension connects to a configured service Native app  recei