---
lang: en
title: 'API docs: context.transformvalueorpromise'
keywords: LoopBack 4.0, LoopBack 4
sidebar: lb4_sidebar
permalink: /doc/en/lb4/apidocs.context.transformvalueorpromise.html
---

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[Home](./index.md) &gt; [@loopback/context](./context.md) &gt; [transformValueOrPromise](./context.transformvalueorpromise.md)

## transformValueOrPromise() function

Transform a value or promise with a function that produces a new value or promise

<b>Signature:</b>

```typescript
export declare function transformValueOrPromise<T, V>(valueOrPromise: ValueOrPromise<T>, transformer: (val: T) => ValueOrPromise<V>): ValueOrPromise<V>;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  valueOrPromise | <code>ValueOrPromise&lt;T&gt;</code> | The value or promise |
|  transformer | <code>(val: T) =&gt; ValueOrPromise&lt;V&gt;</code> | A function that maps the source value to a value or promise |

<b>Returns:</b>

`ValueOrPromise<V>`


