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# isLeft

> **isLeft**\<`T`, `U`>(`e`): `e is Left<T>`

## Type Parameters

| Type Parameter |
| -------------- |
| `T`            |
| `U`            |

## Parameters

| Parameter | Type                                                   |
| --------- | ------------------------------------------------------ |
| `e`       | [`Either`](../../types/type-aliases/Either)\<`T`, `U`> |

## Returns

`e is Left<T>`

## Defined in

[src/modules/utils.ts:42](https://github.com/forte-service-company-ltd/forte-rules-engine-sdk/blob/5aad4d7c3c8cc91280e4449c17ac8ea31219fbed/src/modules/utils.ts#L42)