How should I start to get deep into the project?

I am not that familiar with the js language and any js project.
But I'm now quite interested in the Cesium.
Thus I want to fork one in the and make some modification on it to get own thoughts working.

However, I have been trying to trace the process of the terrian(from downloading to displaying) for a few days; to my regret, i get no door to get in.

So, I am posting to look for some help or some suggestions,
about: 1) how should i get a clue to trace into the system or where should i start
       2) any recommendations about reading js project

Thank you!!

First make sure you’re using the unminified version of the cesium library during development. It’s located in the ‘Build/CesiumUnminified’ directory of the downloaded package. It includes both more debug information and will allow you to set breakpoints in the code using your browser’s developer tools.

I would also recommend downloading a trail of WebStorm. It has an integrated Node debugger that may provide you a more familiar debugging experience.

We also have some recommended reading on the Wiki that will assist you in getting started with understanding the how and why we do things the way we do.’s-Guide