---
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title: unionItems
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description: MuleSoft Documentation Site
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---
---
product: DataWeave
version: 2.13
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---

# unionItems

> For the full documentation index, see: https://docs.mulesoft.com/llms.txt

## unionItems(t: Type): Array<Type>

Returns an array of all the types that define a given Union type. This function fails if the input
is not a Union type.

_Introduced in DataWeave version 2.3.0._

### Parameters

<table><colgroup><col> <col></colgroup><thead><tr><th>Name</th><th>Description</th></tr></thead><tbody><tr><td><p><code>t</code></p></td><td><p>The type to check.</p></td></tr></tbody></table>

### Example

This example shows how `unionItems` behaves with different inputs.

#### Source

```DataWeave
%dw 2.0
import * from dw::core::Types
type AType = String | Number
output application/json
---
{
   a: unionItems(AType)
}
```

#### Output

```Json
{
  "a": ["String","Number"]
}
```