Webpack does that with chunk hash. Common chunks go into common.js, and my app goes into app.js, if I change my app's JS, only app.js gets downloaded which is p

Webpack does that with chunk hash. Common chunks go into common.js, and my app goes into app.js, if I change my app's JS, only app.js gets downloaded which is probably 50kb whereas common.js is maybe 300kb. The point is there is a tradeoff between speed & efficiency. If every line of code were its own file, you'd have a high amount of efficiency when only 1 line changes, but loading that would be a nightmare on mobile.