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

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[Home](./index.md) &gt; [@loopback/context](./context.md) &gt; [ContextObserver](./context.contextobserver.md) &gt; [filter](./context.contextobserver.filter.md)

## ContextObserver.filter property

An optional filter function to match bindings. If not present, the listener will be notified of all binding events.

<b>Signature:</b>

```typescript
filter?: BindingFilter;
```