This, I think is just a library or archive (in the ar/ranlib sense; https://sourceware.org/binutils/docs/binutils/ar.html#ar) of code that the browser loads over the Internet.

Java hit a jackpot calling such a thing a jar, a word that is both shorthand for "Java archive" and a noun describing a container. That suggests looking at words such as 'bottle', 'box', 'cask', 'pot' (nice word, but its connotations do not make it a winner), 'cup', 'amphora', 'pithos' (not well-known enough, and typically unmovable), 'crate' (taken by rust), or 'vase' but I can't find a nice alternative interpretation as an abbreviation ('Jug' has a 'j' that could mean JavaScript, but I think we would be looking for something with a W for 'web' or I for 'internet') or even something that sounds good ('crate' is growing on me, but already taken by rust. That shows that other terms might grow to become acceptable, too. Maybe 'jug' could be such a word?)