> For the complete documentation index, see [llms.txt](https://docs.jentis.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.jentis.com/jentis-dcp-elements/functions-transformations.md).

# Functions (Transformations)

The TWIN-Browser JENTIS technology allows you to run JavaScript functions on the server and client side. It empowers your setup to run custom data operations within the runtime of a virtual environment, such as persisting information on a machine's local storage or applying complex logic or processing with the full capability of a programming language. The backbone for the TWIN is NodeJS.

JENTIS DCP functions apply further logic to customize data to your implementation's use case. These functions are used in tag configurations to apply to specific variables (values). They help transform values before they are submitted in a tag, for example, shortening a string, putting all characters in lower or upper case, or hashing the submitted value.

{% hint style="warning" %}
**Clientside and Serverside Warning**

Please be aware that the transformation functions use different runtimes and scopes based on the tag's execution. If a tag is executed server-side, it is in an ES6 environment capable of resolving asynchronous functions. However, client-side code is more restricted. Beware not to use the same transformation function on both server-side and client-side tags.
{% endhint %}


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