Question

I’m currently experimenting on self replicating code. Out of love for the language I’d like to write it in javascript.

I’m working on a program that writes a function’s code which in turn writes its function own code and so on. Basically, the desired process is this:

1. I manually create A function which returns code (which includes some randomness) and a numeric value (proposed solution to a problem).
2. I call this function a number of times, evaluate the results of each of those returned functions, and continue the process until I have code that is sufficiently good for what I’m trying to do.

Now, I have always been told how eval is evil, how never to use it and so on. However for my specific use case it seems like the Function constructor or eval are exactly what I’m looking for.

So, in short the question is:

Are eval/Function constructor indeed the best tools to use in my case? If so, I figured I’d use the Function constructor to scope the code executed, but is there a way to truly limit it from accessing the global scope? Also, what are some good practices for eval usage in my case?

Answer 1

I think I just figured out something I could use:

If I run my javascript code using node.js I can use the vm module which allows me to execute javascript code safely in a new context, and without letting the executed code have any access to the local or global scopes.

vm.runInNewContext compiles code, then runs it in sandbox and returns the result.
Running code does not have access to local scope. The object sandbox will be used as
the global object for code. sandbox and filename are optional, filename is only used in
stack traces.

You can see a full example here: vm.runInNewContext

This will allow me to eval code safely, and seems to be the safest way (I found) currently available. I think this is a much better solution than eval or calling the Function constructor.

Thank you everyone who helped.