combineFields

[secundant]

const fields = combineFields({
  fields: {
    name: createField({ defaultValue: '' }),
    age: createField({ defaultValue: 0 })
  }
});

const nested = combineFields({
  fields: {
    a: createField({ defaultValue: 'foo' as const }),
    b: combineFields({
      fields: {
        c: combineFields({
          fields: {
            d: createField({ defaultValue: 'bar' as const })
          }
        })
      }
    })
  }
});

sample({
  clock: buttonClicked,
  source: $external,
  fn: external => ({ b: { c: { d: external } } }),
  target: nested.change
});