@loopback/docs/site/apidocs/openapi-v3.mergeopenapispec.md

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---
lang: en
title: 'API docs: openapi-v3.mergeopenapispec'
keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI
sidebar: lb4_sidebar
editurl: https://github.com/loopbackio/loopback-next/tree/master/packages/openapi-v3
permalink: /doc/en/lb4/apidocs.openapi-v3.mergeopenapispec.html
---

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[Home](./index.md) &gt; [@loopback/openapi-v3](./openapi-v3.md) &gt; [mergeOpenAPISpec](./openapi-v3.mergeopenapispec.md)

## mergeOpenAPISpec() function

The default merge function to patch the current OpenAPI spec. It leverages module `json-merge-patch`<!-- -->'s merge API to merge two json objects. It returns a new merged object without modifying the original one.

A list of merging rules can be found in test file: https://github.com/pierreinglebert/json-merge-patch/blob/master/test/lib/merge.js

<b>Signature:</b>

```typescript
export declare function mergeOpenAPISpec<C extends Partial<OpenApiSpec>, P extends Partial<OpenApiSpec>>(currentSpec: C, patchSpec: P): C & P;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  currentSpec | C | The original spec |
|  patchSpec | P | The patch spec to be merged into the original spec |

<b>Returns:</b>

C &amp; P

A new specification object created by merging the original ones.