# `Isbn`

A book's number, in its 13 digits with no hyphens.

Use it for books. For other retail products, use [`Ean13`](/docs/types/type-ean13.md).

## Shape

One value, held as text in one set form, with no parts: `9791090636071`.

## Example

```jadpo
Isbn("9780306406157")
```

`Isbn(raw)` checks the text, and text that isn't one breaks the `format` rule.

`text.parse(raw, as: Isbn)` reads one from text that comes from outside. Text that isn't one at all fails `malformed`, such as `9780306406158`, `0306406152` or `978-0-306-40615-7`.

## Good to know

- A 10-digit ISBN is refused, so convert it first. Remove any hyphens as well.
- `==` tells you whether two are the same. `<` and `list.sort_by` don't take it.

## In JSON

A string, in a request, a response or `json.write`:

```json
"9780306406157"
"9791090636071"
```

## Details

<details>
<summary>Text form, storage, how it is shown, and operations</summary>

`Isbn` is in the group Commerce and logistics, and has been in Jadpo since 0.1.0.

### Text form

`text.from` writes one standard text form, the same form `text.parse` reads back: `9780306406157` and `9791090636071`.

### How it is stored

It is stored in one column named for the field, of type `text`. `9791090636071` is stored as `'9791090636071'`.

### How it is shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `9780306406157` | `9780306406157` |
| `9791090636071` | `9791090636071` |

### Operations

It also takes `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. [How every standard type behaves](/docs/every-standard-type-meets-one-contract.md) says how they work.

</details>