> ## Documentation Index
> Fetch the complete documentation index at: https://docs.membrane.agency/llms.txt
> Use this file to discover all available pages before exploring further.

# Function Types

Function types determine how integration logic is implemented. Each [Action](/docs/how-membrane-works/actions) and [Flow](/reference/workspace-elements/flows) node uses a function type.

| Function Type                                                                                        | Description                                          |
| ---------------------------------------------------------------------------------------------------- | ---------------------------------------------------- |
| [JavaScript](/docs/references/functions/function-types/javascript)                                   | Run custom JavaScript/TypeScript logic               |
| [Mapping](/docs/references/functions/function-types/mapping)                                         | Transform data using declarative field mappings      |
| [REST API Mapping](/docs/references/functions/function-types/rest-api-mapping)                       | Map fields to REST API request parameters            |
| [GraphQL API Mapping](/docs/references/functions/function-types/graphql-api-mapping)                 | Map fields to GraphQL queries and mutations          |
| [API Request to External App](/docs/references/functions/function-types/api-request-to-external-app) | Make authenticated requests to a connected app's API |
| [API Request to Your App](/docs/references/functions/function-types/api-request-to-your-app)         | Make requests to your backend's Internal API         |
| [HTTP Request](/docs/references/functions/function-types/http-request)                               | Make arbitrary HTTP requests                         |
| [Run Action](/docs/references/functions/function-types/run-action)                                   | Execute another action                               |