# Typing

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This is the official documentation of the `@forestadmin/agent` Node.js agent.
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Fields on Forest Admin can either use `Primitive Types` or `Composite Types`.

### Primitive types

The primitive types which are supported by Forest Admin are the following:

| Forest Admin Type | Language Type                                              |
| ----------------- | ---------------------------------------------------------- |
| Boolean           | Boolean                                                    |
| Date              | String with format "1985-10-26T01:22:00-08:00Z" (ISO-8601) |
| Dateonly          | String with format "1985-10-26"                            |
| Enum              | String                                                     |
| JSON              | Any JSON compatible value                                  |
| Number            | Number                                                     |
| Point             | Array of 2 Numbers                                         |
| String            | String                                                     |
| Timeonly          | String with format "01:22:00"                              |
| Uuid              | String with uuid v4 format                                 |

### Composite types

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* Fields using composite types are not sortable and do not implement validation.
* Fields that are an array of a primitive type **only** are filterable (depending on the data source).
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```js
// Object containing 2 strings
const typeOfObjectWithTwoStrings = { firstName: 'String', lastName: 'String' };

// Array of strings
const typeOfArrayOfStrings = ['String'];

// Array of objects
const typeOfArrayOfObjects = [{ content: 'String' }];

// Object containing a 2d-grid of numbers
const typeOfObjectContainingAGridOfNumbers = { content: [['Number']] };
```

When using composite types, the data in the UI may not be displayed as you expect!

| Composite Type                        | Example                                         | How it gets displayed                       |
| ------------------------------------- | ----------------------------------------------- | ------------------------------------------- |
| Array of primitive type               | `[ 'array', 'of', 'strings']`                   | As a custom widget in the edition form      |
| Object                                | `{ title: "the godfather"}`                     | As a nested form in the edition form        |
| Array of object                       | `[{ title: "the shawshank redemption"}]`        | As a new collection in Related Data section |
| Array of object (with nested objects) | `[{ rating: { kind: 'MPA", value: "PG-13" } }]` | JSON editor in the edition form             |
| Anything else                         |                                                 | JSON editor in the edition form             |

If you want to force displaying your data as a new Collection in the Related Data section, but can't because your data model contains nested objects, you may consider typing all nested objects as `'JSON'`.