Can't open main.js?

[CalvinLol777]

Title says it all. I downloaded all the files (except for the models I'm not using) [which I am currently using gemini], and cannot open the main.js file. It will open very briefly, and then put out an error message that goes away too quickly for me to read. By spamming enter on it and force opening it multiple times, I was able to catch bits of the error message. It says something about not able to find or load the main class, and then what I think is the directory for the mindcraft file? I'm not exactly sure what to make of this, but if anyone could help, it'd be greatly appreciated.