执行二进制代码

I'm designing a game and have a somewhat unique problem.

To play the game, players each write a simple javascript program that continually makes a request of my backend for the game state and then decides what to do and posts their move (also to my backend).

I want to store the user scripts on my end though, so I've given them the option to upload their scripts with the standard HTML5 input type="file". Then I use FileReader to read in the raw binary, and associate that binary input as a "bot" for the user in Mongo. (My backend is written in Go)

Docs for FileReader:
https://developer.mozilla.org/en-US/docs/Web/API/FileReader

So far, I've found a resource for converting the binary back to ascii:
Converting Binary to text using javascript

I found a javascript interpreter that I can allegedly execute javascript from: https://github.com/jterrace/js.js

In this situation, is there a better way to run the uploaded code, perhaps as an executable? Is a javascript sandbox solution like JSJS overkill?

It should always be a good idea to sandbox any user submitted code, regardless if it's executed on the client or server.