---
url: "https://vueda.dev/v3/reference/api/js/use/themeRegistry/functions/setClassMerger.md"
title: "setClassMerger"
---

# setClassMerger

## Overview

Register the active theme's CSS conflict rules. Pass null to restore plain
class combining. Theme data and the merger are configured independently.

## Signature

`setClassMerger(merger)`

### Parameters

| Name | Type | Required | Description |
| --- | --- | --- | --- |
| <span id="param-merger">merger</span> | `(classes: string) => string` | yes | Receives active classes after false-key removals. |

### Returns

`void`

## Source

`client/lib/use/themeRegistry.js:48`