***

id: 12da04cf-5f2c-4755-8b2e-0d67439e6d05
title: Utility functions
slug: /js/reference/signalwire/utils
max-toc-depth: 3
----------------

## `buildVideoElement`

* **buildVideoElement**(`options`): `Promise<BuildVideoElementReturnType>`

A function that creates and optionally injects a video DOM element for a given Call or Room object.

<Tip>
  If you have passed a `rootElement` when [instantiating the SignalWire client](/docs/browser-sdk/v3/js/reference/signalwire/client#instantiation), or
  when [`dial`](/docs/browser-sdk/v3/js/reference/signalwire/client#dial)ing a call, the SDK will manage the DOM automatically; injecting the resulting video stream
  into the `rootElement` that you specified.

  But for more fine grained control, or if you're using a library like React, you can choose to
  manually manage DOM using this function. Be sure to not specify a `rootElement` at instantiation or during dialing.
</Tip>

#### Parameters

| Name                             | Type                                                                                                 | Required? | Description                                                                                                                                                                                          |
| :------------------------------- | :--------------------------------------------------------------------------------------------------- | :-------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `options`                        | `object`                                                                                             | Required  |                                                                                                                                                                                                      |
| `options.room`                   | [`CallFabricRoomSession`](/docs/browser-sdk/v3/js/reference/signalwire/client#callfabricroomsession) | Required  | The Call Fabric Room Session to build the video element for                                                                                                                                          |
| `options.rootElement`            | `HTMLElement`                                                                                        | Optional  | The HTML container element which will contain the video stream. If `rootElement` is not passed, the resulting DOM element will be returned, and can be injected into any container element manually. |
| `options.applyLocalVideoOverlay` | boolean                                                                                              | Optional  | Whether to apply local video overlays on the remote stream                                                                                                                                           |

#### Response

| Name                   | Type          | Description                                                                                                                                                           |
| :--------------------- | :------------ | :-------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `response`             | `object`      | -                                                                                                                                                                     |
| `response.element`     | `HTMLElement` | The container for the stream. If `rootElement` was not passed, this is a newly created container. Otherwise, it is the same as the `rootElement` which was passed in. |
| `response.unsubscribe` | `()=>void`    | Call this function to turn off all event handling for the stream before disposing of the container element.                                                           |

#### Example

After the [SignalWire Client](/docs/browser-sdk/v3/js/reference/signalwire/client) has been [instantiated](/docs/browser-sdk/v3/js/reference/signalwire/client#instantiation), you can
dial a video call and inject it into the DOM as follows:

```js
const call = await client.dial({
  /* ... */
});

await call.start();

const { element, unsubscribe } = await buildVideoElement({
  room: call,
});
const container = document.getElementById("container");
container.appendChild(element);
```

Alternatively, you can pass in the `rootElement` parameter and let the function automatically manage DOM:

```js
const { element, unsubscribe } = await buildVideoElement({
  room: call,
  rootElement: document.getElementById("container"),
});
```