How to pass actual values to minimist instead of key-value?

https://www.npmjs.com/package/minimist

For some keys I want to be able pass actual variables of them instead:

$ node my_script.js --var1 a --var2 b --var3 c

===>

$ node my_script.js --var1 a --b --var3 c
$ node my_script.js --var1 a --b1 --var3 c
$ node my_script.js --var1 a --b2 --var3 c

Where (b, b1, b2, ... bN) — is a predefined set of constants.

How to do it? Is it possible at all?