What kind of JS data structure internals represent?

Question

I am looking at celebrate.js . Object internals

internals
{
  DEFAULT_ERROR_ARGS: { celebrated: true },
  DEFAULT_ERRORS_OPTS: { statusCode: 400 },
  DEFAULT_CELEBRATE_OPTS: { mode: 'partial' }
}

Different actions are applied to this object later.

internals.validateSegment = (segment) => (spec, joiConfig) => {
  const finalValidate = (req) => spec.validateAsync(req[segment], joiConfig);
  finalValidate.segment = segment;
  return finalValidate;
};

What do internals represent?

Answer 1

The internals object holds a set of default options (called segments here). They are accessed by their identifiers DEFAULT_ERROR_ARGS , DEFAULT_ERRORS_OPTS and DEFAULT_CELEBRATE_OPTS .

The segments are object themselves, that contain options (eg celebrated ) and their default values (eg true ).

All segments of internals can be passed to and validated by validateSegment() . Each property is defined by a key (here: spec ) and a value (here: joiConfig ). For each specification the function validateAsync() is called and the result is assigned to finalValidate .

The function validateSegment() can be called for individual segments. See function maybeValidateBody() in the code that you linked to, for example:

internals.maybeValidateBody = (segment) => {
  const validateOne = internals.validateSegment(segment); <-- Called here!
  return (spec, joiConfig) => {
  ...

In the above code block, the segment is passed to internals.validateSegment() and the return value is assigned to validateOne , for example.