---
lang: en
title: 'API docs: context.contextobserverfn'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/context
permalink: /doc/en/lb4/apidocs.context.contextobserverfn.html
---

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[Home](./index.md) &gt; [@loopback/context](./context.md) &gt; [ContextObserverFn](./context.contextobserverfn.md)

## ContextObserverFn type

Listen on `bind`<!-- -->, `unbind`<!-- -->, or other events

**Signature:**

```typescript
export type ContextObserverFn = (eventType: ContextEventType, binding: Readonly<Binding<unknown>>, context: Context) => ValueOrPromise<void>;
```
**References:** [ContextEventType](./context.contexteventtype.md)<!-- -->, [Binding](./context.binding.md)<!-- -->, [Context](./context.context.md)<!-- -->, [ValueOrPromise](./context.valueorpromise.md)