replace undefined environment variables with undefined

[tjconcept]

fixes #11

[hughsk]

Thanks for the patch @tjconcept! I'm curious though, what's the benefit in replacing these values with undefined? They already evaluate to undefined at runtime, even without envify:

$ echo 'console.log(process.env.NODE_ENV)' | browserify - | node
undefined

Additionally, there are some cases where you don't want envify to touch environment variables that haven't been set, leaving them for a second envify transform step to take care of.

[tjconcept]

I think it's cleaner, and I can avoid stubbing the process variable all together.
I hadn't thought of the "double use" use case though..

[hughsk]

@tjconcept I don't think you need to worry about the cleanliness of your code once it's been through browserify :) If you want to explicitly remove the variable to avoid all of the process shim getting pulled in, you should be able to do:

browserify -t [ envify --no-NODE_ENV ]

Which will replace process.env.NODE_ENV with false. Would that fix your issue?

[tjconcept]

Yes it would, but I would also have to specify 4-5 other variables.
My use case is client applications which communicate with several web services and 95% of the time the build just goes with the default values, but it's necessary to configure each of these in a production environment or while cross-developing a feature in a service and in the client.

Maybe this could be added as optional? I still think it is the "expected" behavior though, as @Naman34 in #11 did.

[hughsk]

@tjconcept, @Naman34, I've gone ahead and implemented this as an optional feature. You should be able to use it by adding purge as an argument to envify:

browserify -t [ envify purge --NODE_ENV development ]

More details in the readme :)

[nmn]

Thanks!