> For the complete documentation index, see [llms.txt](https://docs.agilecase.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.agilecase.com/administrator-documentation/types-of-custom-field/javascript-label.md).
# JavaScript Label
The JavaScript label field type allows you to enter your own javascript commands that function within the tab. The script shown above will calculate the age of a client based on their date of birth.
JavaScript fields can be used in a variety of ways: they can carry out calculations, edit the UI and provide advanced formatting options dependent on the values saved in the fields present in the tab. Unlike on save and on load scripting, JavaScript labels only function in the tab they are present in, so cannot be used when creating documents or reports.
This screenshot shows the field above in the contact tab. The calculation is carried out using the "Date of Birth" field above and the result is displayed in the JavaScript field.
To see what else you can do with JavaScript labels, and how to write the script itself, see [Custom Form Scripting](/developer-documentation/custom-form-scripting.md) in the developer documentation.
If you have any trouble creating your own fields or would like to implement JavaScript labels but lack the technical knowledge to do so, please get in touch at for more information and pricing.
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