conformer

Usage: conformer(f, unf)

Takes a predicate function with the semantics of conform i.e. it should return either a (possibly converted) value or ':node.spec/invalid', and returns a spec that uses it as a predicate/conformer. Optionally takes a second fn that does unform of result of first

Source

Example:

const s = require('speculaas');
const {invalidString, isInteger} = s.utils;

const pred = value => isInteger(value) ? value : invalidString;
const spec = s.conformer(pred);

s.isValid(spec, 13);
// true

s.isValid(spec, '13');
// false