Intercept requests and modification of the server response

[trtty]

Smoke, you would like to inject js's only in one project or you want to build a tool for this?

If 2nd, there is no need in hooking APIs... Build LSP library and add all required data to the packet.

[Evilcry]

Try also to take a look on how work ZeuS (source code for version 2.0.8.9) are available, you can check how WebInjection is managed.