---
title: "errorMonitor | JavaScript maps SDK"
description: "Documentation for MapTiler SDK"
---

> For AI agents: a documentation index is available at [/llms.txt](https://docs.maptiler.com/llms.txt). Markdown versions of all pages are available by appending .md to any URL.

# Variable errorMonitor`Const`

errorMonitor: unique symbol

This symbol shall be used to install a listener for only monitoring `'error'` events. Listeners installed using this symbol are called before the regular `'error'` listeners are called.

Installing a listener using this symbol does not change the behavior once an `'error'` event is emitted. Therefore, the process will still crash if no regular `'error'` listener is installed.

#### Since[](#since)

v13.6.0, v12.17.0