[API reference](https://evolu.dev/docs/api-reference) › [@evolu/common](https://evolu.dev/docs/api-reference/common) › [Type](https://evolu.dev/docs/api-reference/common/Type) › UniqueError

Defined in: [packages/common/src/Type.ts:13346](https://github.com/evoluhq/evolu/blob/bc4578a260dd15d5bbf94b83765ca05984d194cb/packages/common/src/Type.ts#L13346)

Error returned when [unique](https://evolu.dev/docs/api-reference/common/Type/functions/unique) finds equal items.

`index` locates the first item equal to an earlier item, and `previousIndex`
locates the earliest item it equals.

## Extends

- [`TypeError`](https://evolu.dev/docs/api-reference/common/Type/interfaces/TypeError)\<`"Unique"`\>

## Properties

<a id="index"></a>

### index

```ts
readonly index: number;
```

Defined in: [packages/common/src/Type.ts:13348](https://github.com/evoluhq/evolu/blob/bc4578a260dd15d5bbf94b83765ca05984d194cb/packages/common/src/Type.ts#L13348)

---

<a id="previousindex"></a>

### previousIndex

```ts
readonly previousIndex: number;
```

Defined in: [packages/common/src/Type.ts:13349](https://github.com/evoluhq/evolu/blob/bc4578a260dd15d5bbf94b83765ca05984d194cb/packages/common/src/Type.ts#L13349)

---

<a id="type"></a>

### type

```ts
readonly type: "Unique";
```

Defined in: [packages/common/src/Type.ts:1005](https://github.com/evoluhq/evolu/blob/bc4578a260dd15d5bbf94b83765ca05984d194cb/packages/common/src/Type.ts#L1005)

#### Inherited from

[`TypeError`](https://evolu.dev/docs/api-reference/common/Type/interfaces/TypeError).[`type`](https://evolu.dev/docs/api-reference/common/Type/interfaces/TypeError#type)

---

<a id="value"></a>

### value

```ts
readonly value: readonly Data[];
```

Defined in: [packages/common/src/Type.ts:13347](https://github.com/evoluhq/evolu/blob/bc4578a260dd15d5bbf94b83765ca05984d194cb/packages/common/src/Type.ts#L13347)