Well your post consisted of two questions.
1. where is the code
runtime.js after exporting.
2. Read the code
Here seems to be the the answer that's not being express well. The runtime.js is in pure English javascript code. It's as close to human visualization and readability as it can get. It's not in machine language, but in the language that some one with an editor would type out.
The difference being is that C2 write's the code in an effecient form that isn't meant to be read by humans. It's still the same language, but it's as note and abbreviated form. In a pattern that the browser can interpret.
That is the code created. There isn't anything else except for the source of exporter to js itself. Which is closed source.