must-lookup-prop-in-dict-pmb

Look up the value of some config object's property in a dictionary object, throw if not found. (Double lookup, double throw.)

API

This module exports one function:

lookup(descr, cfg, dict, key, dflt)

First, look up the option value, i.e. cfg[key] if it exists, otherwise dflt will be used as the option value.

• The idea is that the option value is something that makes sense to a human reader, e.g. presentation.
• The option value cannot be undefined (the false-y value). This should not be a problem, as it would be stringified for dict lookup anyway, so you can use the string 'undefined'.
• If cfg is a function, the option value will instead be determined by cfg(key, dflt). A result of undefined means failure.
  • This feature works nicely with the .ifHas from objpop.

Once the option value is determined, translate it by dict to an actionable representation, and return that, e.g. { HandleLidSwitch: 'ignore', IdleAction: 'ignore' }.

If either lookup fails, throw an error. The error message will use String(descr || dict) as the (hopefully) human-readable context description.

Usage

see the tests.

Known issues

• Needs more/better tests and docs.

 

License

ISC