---
title: "Function JavaScript"
description: "define custom JavaScript functions"
source: "https://github.com/log-10x/modules/tree/main/pipelines/run/units/transform/script/function/unit.yaml"
icon: "material/function"

---
## :material-menu: Options

Specify the options below to [configure](/config "configure") multiple Function JavaScript:

|Name|Description|
|---|---|
|[functionFuncName](#functionfuncname "JavaScript function name")|JavaScript function name|
|[functionClassName](#functionclassname "JavaScript class name")|JavaScript class name|
|[functionType](#functiontype "specify the type of function")|Specify the type of function|
|[functionActions](#functionactions "function statements")|Function statements|
|[functionFile](#functionfile "Declaring .js file")|Declaring .js file|

### :material-menu-right-outline:**`functionFuncName`**

JavaScript function name.

|Type|Required|
|---|---|
|String|✔|

JavaScript statements for initializing target input(s) TenxTemplates.

**NOTE**: This argument is not designed to be set directly, but instead by passing a [.js launch file](https://doc.log10x.com/config/javascript/) containing
these statements nested within an [TenXObject](https://doc.log10x.com/api/js/#TenXObject "Provide structured, reflective access to log/trace events read from input(s).") sub-class constructor as command line argument as described above.


### :material-menu-right-outline:**`functionClassName`**

JavaScript class name.

|Type|Required|
|---|---|
|String|✔|

JavaScript statements for initializing target input(s) TenxTemplates.

**NOTE**: This argument is not designed to be set directly, but instead by passing a [.js launch file](https://doc.log10x.com/config/javascript/) containing
these statements nested within an [TenXObject](https://doc.log10x.com/api/js/#TenXObject "Provide structured, reflective access to log/trace events read from input(s).") sub-class constructor as command line argument as described above.


### :material-menu-right-outline:**`functionType`**

Specify the type of function.

|Type|Required|
|---|---|
|String|✔|

|Context|Description|Execution Timing|Purpose|Example Use Case|
|---|---|---|---|---|
|Instance|Refers to custom subclasses of `TenXObject` or similar instance-level classes, where code operates on individual data instances (e.g., events or objects).|Executed for each instance created during pipeline processing (high-volume, per-event).|To enrich, filter, or transform specific data instances at runtime, with access to instance properties via `this`.|In a log processing pipeline, extend `TenXObject` to add a custom field like `this.enrichedLevel = TenXString.toUpperCase(this.level)`.|
|Static|Static methods or getters in subclasses (e.g., `static shouldLoad()`), which are class-level and don't require an instance.|Called early, before instantiation (e.g., during loading or decision-making phases).|For configuration checks, conditional loading, or class-level utilities without per-instance overhead.|Use `static shouldLoad(config)` to decide if a subclass should be applied based on env vars, like `return !config.quiet`.|
|Summary|Custom subclasses of `TenXSummary`, which aggregate values across multiple instances.|Executed after aggregation phases (e.g., at intervals or after a batch of events).|To compute and access summaries like averages, counts, or metrics from grouped data.|Extend `TenXSummary` to calculate custom metrics, e.g., `this.avgResponseTime = this.sumResponseTime / this.count`.|
|Template|Custom subclasses of `TenXTemplate`, defining schemas or structures for other objects.|Executed during initialization or when templates are loaded/created.|To customize the structure/schema of data objects, often for validation or formatting.|Extend `TenXTemplate` to define a custom log format, e.g., adding fields like `timestamp` and `level`.|
|Input|Custom subclasses of `TenXInput`, handling data ingestion.|Executed once per pipeline run, during input setup (low-cardinality).|To customize how data is read or ingested, with access to input-specific config.|Extend `TenXInput` to read from a custom source, e.g., `if (this.inputPath) { this.loadFile(this.inputPath); }`.|
|Output|Custom subclasses of `TenXOutput`, managing data output.|Executed once per pipeline run, during output setup (low-cardinality).|To customize data writing, formatting, or transmission, with access to output config.|Extend `TenXOutput` to log to a file, e.g., `TenXConsole.log("Writing to: " + this.outputFilePath)`.|
|Unit|Custom subclasses of `TenXUnit`, representing pipeline components or steps.|Executed during pipeline initialization or per-unit setup (low to medium cardinality).|To initialize or customize pipeline units like loaders or processors.|Extend `TenXUnit` to load configs, e.g., `if (this.unitName === "loadConfig") { TenXConsole.log("Launching..."); }`.|


### :material-menu-right-outline:**`functionActions`**

Function statements.

|Type|Required|
|---|---|
|List|✔|

JavaScript function statements.

**NOTE**: This argument is not designed to be set directly, but instead by passing a [.js launch file](https://doc.log10x.com/config/javascript/) containing
these statements nested within an [TenXObject](https://doc.log10x.com/api/js/#TenXObject "Provide structured, reflective access to log/trace events read from input(s).") sub-class constructor as command line argument as described above.


### :material-menu-right-outline:**`functionFile`**

Declaring .js file.

|Type|Default|
|---|---|
|String|""|

Specifies the .js file name declaring [functionActions](https://doc.log10x.com/run/transform/script/function/#functionactions "function statements").


<br/>:material-github: This unit is defined in [function/unit.yaml](https://github.com/log-10x/modules/tree/main/pipelines/run/units/transform/script/function/unit.yaml "function/unit.yaml"){target="\_blank"}.