clean.array: skipping elements

[IlyaSemenov]

Re: #9 (comment) by @tomanagle:

@IlyaSemenov could there also be a clean.skip method? I sometimes want to allow empty arrays for certain values. A skip method should allow me to define the values that I don't ant to be included in the clean function.

Hmm... Please elaborate with the sample imaginary input, desired output and desired API syntax?

Filtering out values in an array is a reasonable use case, but I'm not sure about the particular API.

At the moment you can do that with either a custom cumulative cleaner:

const cleanArrayEvenValues = clean.array({
  element: clean.integer(), // ensure all elements are integers
  clean: values => values.filter(value => value % 2 === 0) // only keep even values
})

cleanArrayEvenValues([1,2,3,4,5,6,7]).then(res => console.log(res)) // [2,4,6]

or you can delegate the decision to element cleaner, return undefined for unwanted values, and filter them out in the cumulative cleaner:

const cleanArrayEvenValues = clean.array({
  element: clean.integer({
    clean: value => value % 2 === 0 ? value : undefined, // return undefined for unwanted values
  }),
  clean: values => values.filter(value => value !== undefined) // skip undefined elements
})

cleanArrayEvenValues([1,2,3,4,5,6,7]).then(res => console.log(res)) // [2,4,6]

this part clean: values => values.filter(value => value !== undefined) seems to be useful in many circumstances and could be extracted to a helper option like clean.array({ skipUndefined: true }).

Thoughts?