XanoScript for Custom Functions

Introduction

The Custom Functions primitive lets you define reusable logic using XanoScript. Each Custom Function can be inserted into any other place you’re building logic in Xano; even other Custom Functions. Custom Functions will typically:

Declare their name and description
Accept inputs
Run one or more operations in a stack
Return a response (optional)

Anatomy

Every XanoScript Custom Function follows a predictable structure. Here’s a quick visual overview of its main building blocks — from declaration at the top to settings at the bottom.

You can find more detail about each section by continuing below.

Declaration

Every Custom Function starts with a declarative header that specifies its type, name, and description.

XanoScript

// Converts a text string into a camelCase slug by removing special characters, splitting it into words, and then capitalizing the first letter of each word except the first. This is useful for creating clean, programmatic identifiers from user-generated text.
function utilities/create_camel_case_slug {
...
}

Element	Required	Description
`function`	✅	Declares an Custom Function primitive.
`api_name`	✅	The unique path for the custom function (e.g., `utilities/create_camel_case_slug`). Take note of the path defining a folder with utilities/ as well; you can do this to organize your custom functions into folders.
`description`	no	A short summary of the function. May also appear as a “//” comment above the block.

Section 1: Inputs

The input block defines the data that will be sent to the Custom Function. You can declare types, optionality, and filters:

Hover over this image to see the XanoScript version

For each input, you can:

Declare its type (text, email, password, etc.)
Mark it as optional (?)
Apply filters (filters=trim|lower)

Learn more about the available data types

Section 2: Stack

The stack block contains the actual logic that will be executed when the Custom Function is executed.

Hover over this image to see the XanoScript version

Each block inside stack corresponds to a function available in Xano’s visual builder:

conditional — Executes different logic based on a condition
foreach — Loop through a list of items
text.append — Append a value to a text variable
text.capitalize — Capitalize a text value
text.split — Split a text value into an array
text.regex_replace — Replace a text value with a regex
text.to_lower — Convert a text value to lowercase
text.count — Count the number of items in an array
text.slice — Slice an array

The syntax mirrors how you’d configure these functions visually, but expressed textually. The actual behavior is the same — refer to the function’s existing docs for complete details.

Review all available functions and their XanoScript in the function reference

Section 3: Response

The response block defines what data your API returns:

Hover over this image to see the XanoScript version

The value assignment determines the JSON returned by the Custom Function.
Variables captured in the stack (e.g., $camel_case_slug) can be returned here.

Settings

Custom Function primitives support several optional settings that control authentication, tagging, caching, and version history. These settings are defined at the root level of the API block, after the input, stack, and response blocks. They affect how the endpoint behaves, how it’s documented, and how responses are cached.

Setting	Type	Required	Description
`description`	string	no	A human-readable description of the function. This field can also be represented as a comment starting with ”//” right above the function block.
`tags`	array[string]	no	A list of tags used to categorize and organize the API in your workspace.
`history`	object	no	Configures version inheritance and history behavior. `{inherit: true}` allows this API to inherit history settings from the workspace.
`cache`	object	no	Configures caching behavior for this API. See below for supported fields.

The cache block configures caching behavior for the API:

Field	Type	Description
`ttl`	number (seconds)	Time-to-live for cache entries. A value of `0` disables caching.
`input`	boolean	Whether the request body and query parameters are factored into the cache key.
`auth`	boolean	Whether authentication state (e.g., user ID) is included in the cache key.
`datasource`	boolean	Whether the datasource context is factored into the cache key.
`ip`	boolean	Whether the request IP address is included in the cache key.
`headers`	array[string]	A list of headers whose values should be included in the cache key.
`env`	array[string]	A list of environment variables whose values should be included in the cache key.

Detailed Example

Below, you’ll see a complete example of a typical signup API endpoint.

XanoScript

function utilities/create_camel_case_slug {
  description = "Converts a text string into a camelCase slug by removing special characters, splitting it into words, and then capitalizing the first letter of each word except the first. This is useful for creating clean, programmatic identifiers from user-generated text."
  input {
    text text {
      description = "The input text to be converted into a camelCase slug."
    }
  }

stack {
  // Clean and split the input text into an array of words.
  var $words_array {
    value = "/[^a-zA-Z0-9s]/"|regex_replace:"":$input.text|to_lower|split:" "|filter:"return $this != '';"
  }

  // Initialize the slug with the first word.
  var $camel_case_slug {
    value = ""
  }

  conditional {
    if (($words_array|count) > 0) {
      var.update $camel_case_slug {
        value = $words_array|first
      }
    }
  }

  // Get the rest of the words to be processed.
  var $words_array_sliced {
    value = ($words_array|count) > 1 ? ($words_array|slice:1:-1) : []
  }

  foreach ($words_array_sliced) {
    each as $word {
      // Capitalize each subsequent word and append it to the slug.
      text.append $camel_case_slug {
        value = $word|capitalize
      }
    }
  }
}

  response = $camel_case_slug

  tags = ["utility functions"]
}

What’s Next

Now that you understand how to define APIs in XanoScript, here are a few great next steps:

Explore the function reference

Learn about the built-in functions available in the stack to start writing more complex logic.

Try it out in VS Code

Use the XanoScript VS Code extension with Copilot to write XanoScript in your favorite IDE.

Learn about Background Tasks

Similar to APIs and Custom Functions, Tasks are easy to build logic, but they run in the background on a specific schedule.

Start

AI

References

Introduction

Anatomy

Declaration

Section 1: Inputs

Learn more about the available data types

Section 2: Stack

Review all available functions and their XanoScript in the function reference

Section 3: Response

Settings

Detailed Example

What’s Next

Explore the function reference

Try it out in VS Code

Learn about Background Tasks

​Introduction

​Anatomy

​Declaration

​Section 1: Inputs

Learn more about the available data types

​Section 2: Stack

Review all available functions and their XanoScript in the function reference

​Section 3: Response

​Settings

​Detailed Example

​What’s Next

Explore the function reference

Try it out in VS Code

Learn about Background Tasks

Introduction

Anatomy

Declaration

Section 1: Inputs

Section 2: Stack

Section 3: Response

Settings

Detailed Example

What’s Next