By "user" you mean developer, but you're trading off compile time pain for you, and saddling everyone else with downloading an extra 100kb, which on mobile networks or in developing countries is unforgivable.
GWT was the same way, asset packaging was a core feature even in 2009. For example, it would automatically compile CSS, UI templates, and images, auto-optimizing them, and auto-sprite-sheeting everything, while packaging things into as few HTTP requests as possible.
The real issue is that to do this in a safe way for JS requires coding conventions be adhered to, or the adoption of TypeScript and annotations. Closure's advanced mode will break JS that tries to get too fancy with dynamism.