> For the complete documentation index, see [llms.txt](https://docs.adapptio.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.adapptio.com/reference-guide/functions/types.md).

# Types

### Is Null

*Returns true if a value is null.*

#### Expression:

**ISNULL**(*value*: any)

#### Return:

boolean

#### Example of usage:

```javascript
ISNULL("Are my pockets full?")

Return value:
false
```

### Is String

*Returns true if a value is a string.*

#### Expression:

**ISSTRING**(*value*: any)

#### Return:

boolean

#### Example of usage:

```javascript
ISSTRING("Phillips, tested on humans.")

Return value:
true
```

### Is Number

*Returns true if a value is a number.*

#### Expression:

**ISNUMBER**(*value*: any)

#### Return:

boolean

#### Example of usage:

```javascript
ISNUMBER(1234)

Return value:
true
```

### Is Bool

*Returns true if a value is a boolean.*

#### Expression:

ISBOOL(*value*: any)

#### Return:

boolean

#### Example of usage:

```javascript
ISBOOLEAN(true)

Return value:
true
```

### Is Object

*Returns true if a value is an object.*

#### Expression:

**ISOBJECT**(value: any)

#### Return:

boolean

#### Example of usage:

```javascript
ISOBJECT({key1: "apples", key2: "pears"})

Return value:
true
```

### Is Array

*Returns true if a value is an array.*

#### Expression:

**ISARRAY**(*value*: any)

#### Return:

boolean

#### Example of usage:

```javascript
ISARRAY([{key1: "apples"} , {key2: "pears"}])

Return value:
true
```