> For the complete documentation index, see [llms.txt](https://docs.plumvoice.com/fuse/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.plumvoice.com/fuse/data/evaluate-js.md).
# Evaluate JS
{% hint style="danger" %}
**This is an advanced module**
{% endhint %}
## **Function**
This module enables users to write JavaScript and have it execute within the application.\
Anything that can be done in JavaScript can be written in this module.
For example, it can support a mod10 check for an “offline” credit card number change by doing calculations based on the digits input by the caller.
All the JavaScript written in the module is in its own scope. Any variables that are not added via reference will not be considered “global” will be limited locally to that module.
To use application variables or assign variables that will be available outside the JavaScript module, you will need to use the 
button on the lower-right hand corner.
For example:
| Module | Description |
| ------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| 
| In this scenario, `variable_x` (defined by the module name) will have a value of 2. |
| 
| In this scenario, the variable *`result`* will have a value of 4. |
|  | This scenario assigns 10 from the result of `variable_x` + 8 to the variable *`result`*. |
## **Module Settings**
### [Private](/fuse/module-settings.md#private)
| | |
| ------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| 
| This setting controls the logging function of a module.
Enabling the 'Private' setting instructs the module to not record, report, or retain the information input to that module for reporting or any other purposes. When enabled any information entered into a module during a call will be lost immediately when the call terminates.
The 'Private' setting is critical for businesses that need to maintain PCI-DSS or HIPAA compliance.
The module icon, in the upper left-hand corner, becomes grayed-out when this setting is enabled. See more details here.
|
### [**Module Size**](/fuse/module-settings.md#module-size)
| | |
| ------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| 
| This setting allows users to toggle the size of the Fuse module between Small and Large.
This setting only affect size of the module cosmetically in the editor.
|
### [**Show Custom Errors (Evaluate JS)**](/fuse/module-settings.md#show-custom-errors-evaluate-js)
| | |
| ------------------------------------------------------------------- | --------------------------------------------------------------------------------------------- |
| 
| This setting can be used to catch any errors that might occur when evaluating the Javacsript. |
---
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