## JavaScript-only settings { #javascript-only-settings }

Swagger UI also allows other configurations to be **JavaScript-only** objects (for example, JavaScript functions).

FastAPI also includes these JavaScript-only `presets` settings:

```JavaScript
presets: [
    SwaggerUIBundle.presets.apis,
    SwaggerUIBundle.SwaggerUIStandalonePreset
]

# Extra Data Types { #extra-data-types }

Up to now, you have been using common data types, like:

* `int`
* `float`
* `str`
* `bool`

But you can also use more complex data types.

And you will still have the same features as seen up to now:

* Great editor support.
* Data conversion from incoming requests.
* Data conversion for response data.
* Data validation.
* Automatic annotation and documentation.

For example, let's say that you want to have a *path operation* that allows to update items, and returns HTTP status codes of 200 "OK" when successful.

But you also want it to accept new items. And when the items didn't exist before, it creates them, and returns an HTTP status code of 201 "Created".

from fastapi import FastAPI

tags_metadata = [
    {
        "name": "users",
        "description": "Operations with users. The **login** logic is also here.",
    },
    {
        "name": "items",
        "description": "Manage items. So _fancy_ they have their own docs.",
        "externalDocs": {
            "description": "Items external docs",
            "url": "https://fastapi.tiangolo.com/",
        },
    },
]

        You can use [the template](https://github.com/gradle/gradle-issue-reproducer) with a Gradle GitHub action set up to showcase your problem.
        In the rare cases where this is infeasible, we will also accept a detailed set of instructions.
        You can also use [Gradle Project Replicator](https://github.com/android/project-replicator) to reproduce the structure of your project.
    validations:
      required: true
  - type: input

  modelVersion. This is required so that a change from modelVersion 4.0.0 to
  4.1.0 doesn't cause compatibility problems with users who have not upgraded
  their projects. It also allows for a certain amount of legacy support into the
  future. Therefore, we should rename this file from pom.xml in the maven-core
  jarfile to pom-4.0.0.xml (and successive revisions to the base pom made to

                available, instead of erroring out, the dependency result will be
                `None`.

                This is useful when you want to have optional authentication.

                It is also useful when you want to have authentication that can be
                provided in one of multiple optional ways (for example, in a query
                parameter or in an HTTP Bearer token).
                """

# Environment Variables { #environment-variables }

/// tip

If you already know what "environment variables" are and how to use them, feel free to skip this.

///

An environment variable (also known as "**env var**") is a variable that lives **outside** of the Python code, in the **operating system**, and could be read by your Python code (or by other programs as well).

It would also mean that if you get data from the `Request` object directly (for example, read the body) it won't be validated, converted or documented (with OpenAPI, for the automatic API user interface) by FastAPI.

`Manager.RegisterXHandler(handlerID, handler, subroutes...)`.

A `Handler()` function provides an HTTP handler, which should be hooked up to the appropriate route on the server.

On startup, the manager will start connecting to remotes and also starts listening for incoming connections.
Until a connection is established, all outgoing requests will return `ErrDisconnected`.

# Usage

## Single Payload Requests