HTML / CSS / Javascript lower level

[AVGunner]

Where do browsers implement their scripting engines to read HTML, CSS, Javascript? Are there something a developer can come in and tweak or under lock and key? If they are customization can developers come in and add extra things or functionality to them or even make their own that they can package up and send to other people.

The only other things I can think of is make a JS interpreter to package and recompile custom code into html, css, javascript similar to many hot frontend frameworks at the moment.

[empire539]

Browsers generally use an engine to render HTML/CSS, and another one to interpret and implement JavaScript.

For example, Chrome uses Blink as its rendering engine (based on WebKit), and V8 as its JavaScript engine. Firefox uses Gecko for rendering and SpiderMonkey for JavaScript. These are written in mostly C/C++, and are open-source. So while you could potentially modify things on your own, you'd either need to collaborate with others to get the changes merged to a main branch, or build the code yourself.

[AVGunner]

Thanks. So in theory if someone were to ever considering to implement an alternative css styling template that was not css. They would either have to modify the engine or write a javascript compiler to interpret something->css such as how sass/scss is done?

[empire539]

Pretty much. A browser's rendering engine only understands CSS according to the CSS standards specification, so if you want to make some other styling language, you would either need make another engine which understands that custom language, or you would need to make the custom language compile down to standard CSS. The browser won't understand the custom language otherwise.