> ## Documentation Index
> Fetch the complete documentation index at: https://doc.lucidworks.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Query Operations

[localhost link]: http://localhost:3000/docs/4/fusion-server/reference/query-ops/overview

[mintlify link]: https://doc.lucidworks.com/docs/4/fusion-server/reference/query-ops/overview

[old doc.lw link]: https://doc.lucidworks.com/fusion-server/4.2/10910

This section includes reference information for the following topics:
import { LwTemplate } from '/snippets/LwTemplate.jsx';

<LwTemplate />

* **[Custom JavaScript Stages Variables and Parameters](/docs/4/fusion-server/reference/query-ops/custom-javascript-stages-variables-and-parameters)** - The JavaScript Query stage allows you to write a custom processing logic using JavaScript to manipulate search requests and responses. The first time that the pipeline is run, Fusion compiles the JavaScript program into Java bytecode using the JDK’s JavaScript engine. This article describes the variables and parameters used with [custom JavaScript stages](/docs/4/fusion-server/concepts/querying/pipelines/custom-javascript-query-stages).
* **[Solr Query Language Cheat Sheet](/docs/4/fusion-server/reference/query-ops/query-language-cheat-sheet)** - This cheat sheet is a quick reference to the Solr query language. Use this syntax when querying Fusion via the [Query API](/docs/4/fusion-server/reference/api/query/query-api).