# Values

> The types templates work with, and how they print.

Kiln works with ordinary JavaScript values. Your data goes into a template as it is, with no conversion.

## Types

| Kiln | JavaScript |
| --- | --- |
| null | `null` or `undefined`. Kiln treats them the same |
| boolean | `true` or `false` |
| number | A `number`. There is no separate integer type |
| string | A `string` |
| array | An `Array` |
| hash | A plain object, or a `Map` with string keys |
| set | A `Set` |
| date | A `Date` |
| markup | A string marked safe to output. See [Escaping](https://kilnlang.com/docs/language/escaping/) |
| object | A class instance that opts in. See [Safe markup and classes](https://kilnlang.com/docs/api/safe-markup/) |

## True and false

Conditions such as `if` treat these values as false: `null`, `false`, `0`, `NaN`, `""`, an empty array, an empty hash, and an empty set or map. Everything else is true, including `"0"` and `" "`.

page.kiln:

```kiln
{% if tags %}Has tags{% else %}No tags{% endif %}
{% if title %}Has a title{% endif %}
```

Output:

```html
No tags
Has a title
```

## Printing values

When you output a value, Kiln turns it into a string:

| Value | Output |
| --- | --- |
| null | Nothing |
| boolean | `true` or `false` |
| number | The number, as JavaScript writes it |
| string | The string, escaped |
| date | An ISO 8601 date, such as `2026-10-15T09:30:00.000Z` |
| array, hash, set | An error. Use `join`, `json` or a loop |

Printing an array is an error rather than a silent "[object Object]", so mistakes show up straight away. Use [`json`](https://kilnlang.com/docs/filters/strings/#json) to print data for debugging.

## Empty values

Some features check whether a value is empty rather than false. A value is empty if it is null, `false`, `""`, an empty array, an empty hash, or an empty set or map. Unlike false values, `0` is not empty.

page.kiln:

```kiln
{{ stock|default("Unknown") }}
{{ name|default("Anonymous") }}
```

Output:

```html
0
Anonymous
```

The [`default`](https://kilnlang.com/docs/filters/lists/#default) filter and the [`empty`](https://kilnlang.com/docs/tests/#empty) test use this rule.