index.js
function vanilla(key, value) {
  try {
    assert.deepStrictEqual(value, JSON.parse(JSON.stringify(value)))
  } catch (error) {
    assert.fail('non-specced property `' + key + '` should be JSON')
  }
}
function vanilla(key, value) {
  try {
    assert.deepStrictEqual(value, JSON.parse(JSON.stringify(value)))
  } catch (error) {
    assert.fail('non-specced property `' + key + '` should be JSON')
  }
}
/* Assert `value` (which lives at `key`) can be stringified
and re-parsed to the same (deep) value.