Install different version of npm packages in package.json conditionally

Question

I'm developing a web app which uses a private package. In some circumstances, I rather to use the local version of the package or different version of that package.

Is there any solution to indicate to use different version of package in package.json?

ie:

npm install --local

while my package.json looks like:

...
"dependencies": { 
...
    "my_package": if(local) "address_to_local_package/" else "5.6.1"
...
}

Answer 1

npm does not accommodate this (and honestly, probably should not). This seems like the type of thing that is usually handled at runtime via the NODE_ENV environment variable or similar mechanism. The module changes behavior depending on whether NODE_ENV is set to "production" or "development" . (But that's just convention. You can use values like "local" if you want.) So rather than installing different versions of the module, there's a single version that behaves differently based on the value of that environment variable.

If you really want different code bases installed entirely, it will take some effort but you can write a postinstall script for npm to run. Your module then becomes nothing more than a script and then the postinstall figures out what to actually install based on environment variables or maybe a command line flag. This seems brittle to me, though. I'd think hard about if you're solving the right problem here if you go this route. NODE_ENV seems more elegant and conventional.