Added check option

[borodyadka]

Function that will check for should value be flattened or not.

Example:

const SCHEMA = {
    key1: {
        foo: 'foo',
        bar: 'bar'
    },
    key2: {
        $keep: true,
        test: 'test'
    }
};

let r = flat.flatten(SCHEMA, {
    check: (value) => {
        return !(value.$keep);
    }
});

console.log(JSON.stringify(r, null, 2));

Will print:

{
  "key1.foo": "foo",
  "key1.bar": "bar",
  "key2": {
    "$keep": true,
    "test": "test"
  }
}

I'm using it in my schema validator.

[borodyadka]

ping @hughsk

[timoxley]

@H8BIT I've suggested to @richardschneider in #36 that perhaps a mapKeys/mapValues option could a good solution for these types of problems… perhaps it also warrants filterKeys/filterValues?

For these types of things I usually use flat alongside split-object

e.g.

// note this is untested, just pseudo-code that might work
const filteredItems = split(flat(SCHEMA)).filter(({key, value}) => {
  return !value.$keep
})

const r = flat.unflatten(split.join(filteredItems))