php - Is it possible to catch JS and CSS files Magento loads and make it load corresponding local ones instead? -

i have started learn magento's , oberver architecture.
had been thinking if possible prevent magento store loading js , css files in normal way , instead making load locally stored js , css files.

the point of idea have control on third party resource loading and, ideally, the possibility defer js/css resources.

for example, can merge , defer or change js files in page.xml layout normal, want make module see js file loaded , make load js file from, say, var/resources.

third party resources, e.g. trustpilot js, found, intercepted , pointed locally downloaded version of files var/resources.

and complete cake - ability specify insert element on page, before tag.

so can (reasonably?) done magento module? how should go doing that?