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The JavaScript Query stage allows you to write 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. The JavaScript Query stage allows you to run JavaScript functions over search requests and responses by manipulating variables called “request” and “response” which are Request objects and Response objects, respectively.
Users who can create or modify code obtain access to the broader Fusion environment. This access can be used to create intentional or unintentional damage to Fusion.

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The JavaScript Engine Used by Fusion

The default JavaScript engine used by Fusion is the Nashorn engine from Oracle. See The Nashorn Java API for details. In Fusion 5.9.6 and up, you also have the option to select OpenJDK Nashorn. While Nashorn is the default option, it is in the process of being deprecated and will eventually be removed, so it is recommended to use OpenJDK Nashorn when possible. You can select the JavaScript engine in the pipeline views or in the workbenches. Your JavaScript pipeline stages are interpreted by the selected engine. JavaScript engine selector

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JavaScript Query Stage Global Variables

JavaScript is a lightweight scripting language. In a JavaScript stage, Fusion uses the Nashorn engine, which implements ECMAScript version 5.1. Although Nashorn does include some ECMAScript 6 (ES6) features such as let, const, or template strings, Fusion does not enable ES6 by default, so ES6 support is not guaranteed. What a JavaScript program can do depends on the container in which it runs. For a JavaScript Query stage, the container is a Fusion query pipeline.

Global pipeline variables

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request
Request for a Regular Query The request variable contains Solr query information and is referred to as a regular request. A regular query request does not include Search DSL (domain specific language) parameters.
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request
DSL Request The request variable is also used when the query contains parameters for a Search DSL (domain specific language) request.
See Domain Specific Language for more information.
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response
Response for a Regular Query The response variable contains Solr response information, and is used to return information from a regular request. Because a regular request does not include Search DSL (domain specific language) parameters, the response will not return Search DSL results.
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response
DSL Response The response variable is also used to return information from a Search DSL (domain specific language) request.
See Domain Specific Language for more information.
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ctx
Context A map that stores miscellaneous data created by each stage of the pipeline.
Important Use the ctx variable instead of the deprecated _context global variable.
The ctx variable is used to:
  • Pass data from one stage to another
  • Store data that needs to be passed from one custom stage to a later custom stage
The data can differ between stages:
  • If the previous stage changes the data
  • Based on the configuration of each stage
If the data is modified in one stage, it may cause a later stage to function irregularly.
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collection
StringThe name of the Fusion collection being indexed or queried.
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solrServer
BufferingSolrServer The Solr server instance that manages the pipeline’s default Fusion collection. All indexing and query requests are done by calls to methods on this object. See solrClient for details.
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solrServerFactory
SolrClusterComponent
The SolrCluster server used for lookups by collection name which returns a Solr server instance for that collection, e.g. var productsSolr = solrServerFactory.getSolrServer("products");.
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QueryRequestAndResponse
QueryRequestAndResponse Used to create query pipeline requests and responses.
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JSONResponse
JSONResponse Returns list of info as a string.
See Custom JavaScript Query Stage Examples for more information.

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Syntax Variants

JavaScript stages can be written using function syntax. With function syntax, global variables are passed as function parameters.
Support for legacy syntax was removed in Fusion 5.8.

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Function Syntax

function(request,response) {
   request.addParam("foo", "bar");
}
ImportantFunction syntax is used for the examples in this document.

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Global variable logger

The logs are output to the query service logs for custom query stages. Access the Log Viewer and filter on this service to view the information.

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See also

LucidAcademyLucidworks offers free training to help you get started.The Course for JavaScript in Fusion focuses on how to leverage JavaScript in Fusion to build powerful and responsive scripts at index and query time:
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Visit the LucidAcademy to see the full training catalog.