Combobox
Enables users to pick from a list of options displayed in a dropdown.
Overview
The Combobox component combines the functionality of an input field with a dropdown list of selectable options. It provides users with the ability to search, filter, and select from a predefined set of choices.
Key Features
- Keyboard Navigation: Full support for keyboard interactions, allowing users to navigate and select options without using a mouse.
- Customizable Rendering: Flexible architecture for rendering options, including support for grouped items.
- Accessibility: Built with ARIA attributes and keyboard interactions to ensure screen reader compatibility and accessibility standards.
- Portal Support: Ability to render the dropdown content in a portal, preventing layout issues in complex UI structures.
Architecture
The Combobox component is composed of several sub-components, each with a specific role:
- Root: The main container component that manages the state and context for the combobox.
- Input: The input field that allows users to enter search queries.
- Trigger: The button or element that opens the dropdown list.
- Portal: Responsible for portalling the dropdown content to the body or a custom target.
- Group: A container for grouped items, used to group related items.
- GroupHeading: A heading for a group of items, providing a descriptive label for the group.
- Item: An individual item within the list.
- Separator: A visual separator between items.
- Content: The dropdown container that displays the items. It uses Floating UI to position the content relative to the trigger.
- ContentStatic: An alternative to the Content component, that enables you to opt-out of Floating UI and position the content yourself.
- Arrow: An arrow element that points to the trigger when using the
Combobox.Content
component.
Structure
Here's an overview of how the Combobox component is structured in code:
Reusable Components
It's recommended to use the Combobox
primitives to build your own custom combobox component that can be reused throughout your application.
Managing Value State
Bits UI offers several approaches to manage and synchronize the Combobox's value state, catering to different levels of control and integration needs.
1. Two-Way Binding
For seamless state synchronization, use Svelte's bind:value
directive. This method automatically keeps your local state in sync with the component's internal state.
Key Benefits
- Simplifies state management
- Automatically updates
myValue
when the internal state changes (e.g., via clicking on an item) - Allows external control (e.g., selecting an item via a separate button)
2. Change Handler
For more granular control or to perform additional logic on state changes, use the onValueChange
prop. This approach is useful when you need to execute custom logic alongside state updates.
Use Cases
- Implementing custom behaviors on value change
- Integrating with external state management solutions
- Triggering side effects (e.g., logging, data fetching)
3. Fully Controlled
For complete control over the component's value state, use the controlledValue
prop. This approach requires you to manually manage the value state, giving you full control over when and how the component responds to value change events.
To implement controlled state:
- Set the
controlledValue
prop totrue
on theCombobox.Root
component. - Provide a
value
prop toCombobox.Root
, which should be a variable holding the current state. - Implement an
onValueChange
handler to update the state when the internal state changes.
When to Use
- Implementing complex logic
- Coordinating multiple UI elements
- Debugging state-related issues
Note
While powerful, fully controlled state should be used judiciously as it increases complexity and can cause unexpected behaviors if not handled carefully.
For more in-depth information on controlled components and advanced state management techniques, refer to our Controlled State documentation.
Managing Open State
Bits UI offers several approaches to manage and synchronize the Combobox's open state, catering to different levels of control and integration needs.
1. Two-Way Binding
For seamless state synchronization, use Svelte's bind:open
directive. This method automatically keeps your local state in sync with the component's internal state.
Key Benefits
- Simplifies state management
- Automatically updates
myOpen
when the internal state changes (e.g., via clicking on the trigger/input) - Allows external control (e.g., opening via a separate button)
2. Change Handler
For more granular control or to perform additional logic on state changes, use the onOpenChange
prop. This approach is useful when you need to execute custom logic alongside state updates.
Use Cases
- Implementing custom behaviors on open change
- Integrating with external state management solutions
- Triggering side effects (e.g., logging, data fetching)
3. Fully Controlled
For complete control over the component's value state, use the controlledOpen
prop. This approach requires you to manually manage the value state, giving you full control over when and how the component responds to value change events.
To implement controlled state:
- Set the
controlledOpen
prop totrue
on theCombobox.Root
component. - Provide an
open
prop toCombobox.Root
, which should be a variable holding the current state. - Implement an
onOpenChange
handler to update the state when the internal state changes.
When to Use
- Implementing complex open/close logic
- Coordinating multiple UI elements
- Debugging state-related issues
Note
While powerful, fully controlled state should be used judiciously as it increases complexity and can cause unexpected behaviors if not handled carefully.
For more in-depth information on controlled components and advanced state management techniques, refer to our Controlled State documentation.
Opt-out of Floating UI
When you use the Combobox.Content
component, Bits UI uses Floating UI to position the content relative to the trigger, similar to other popover-like components.
You can opt-out of this behavior by instead using the Combobox.ContentStatic
component.
When using this component, you'll need to handle the positioning of the content yourself. Keep in mind that using Combobox.Portal
alongside Combobox.ContentStatic
may result in some unexpected positioning behavior, feel free to not use the portal or work around it.
Custom Anchor
By default, the Combobox.Content
is anchored to the Combobox.Trigger
component, which determines where the content is positioned.
If you wish to instead anchor the content to a different element, you can pass either a selector string or an HTMLElement
to the customAnchor
prop of the Combobox.Content
component.
What is the Viewport?
The Combobox.Viewport
component is used to determine the size of the content in order to determine whether or not the scroll up and down buttons should be rendered.
If you wish to set a minimum/maximum height for the select content, you should apply it to the Combobox.Viewport
component.
Scroll Up/Down Buttons
The Combobox.ScrollUpButton
and Combobox.ScrollDownButton
components are used to render the scroll up and down buttons when the select content is larger than the viewport.
You must use the Combobox.Viewport
component when using the scroll buttons.
Native Scrolling/Overflow
If you don't want to use the scroll buttons and prefer to use the standard scrollbar/overflow behavior, you can omit the Combobox.Scroll[Up|Down]Button
components and the Combobox.Viewport
component.
You'll need to set a height on the Combobox.Content
component and appropriate overflow
styles to enable scrolling.
Scroll Lock
By default, when a user opens the Combobox, scrolling outside the content will be disabled. You can override this behavior by setting the preventScroll
prop to false
.
Highlighted Items
The Combobox component follows the WAI-ARIA descendant pattern for highlighting items. This means that the Combobox.Input
retains focus the entire time, even when navigating with the keyboard, and items are highlighted as the user navigates them.
Styling Highlighted Items
You can use the data-highlighted
attribute on the Combobox.Item
component to style the item differently when it is highlighted.
onHighlight / onUnhighlight
To trigger side effects when an item is highlighted or unhighlighted, you can use the onHighlight
and onUnhighlight
props.
API Reference
The root combobox component which manages & scopes the state of the combobox.
Property | Type | Description |
---|---|---|
type required | enum | The type of combobox. Default: undefined |
value $bindable | union | The value of the combobox. When the type is Default: undefined |
onValueChange | function | A callback that is fired when the combobox value changes. When the type is Default: undefined |
controlledValue | boolean | Whether or not the value is controlled or not. If Default: false |
open $bindable | boolean | The open state of the combobox menu. Default: false |
onOpenChange | function | A callback that is fired when the combobox menu's open state changes. Default: undefined |
controlledOpen | boolean | Whether or not the open state is controlled or not. If Default: false |
disabled | boolean | Whether or not the combobox component is disabled. Default: false |
name | string | The name to apply to the hidden input element for form submission. If provided, a hidden input element will be rendered to submit the value of the combobox. Default: undefined |
required | boolean | Whether or not the combobox menu is required. Default: false |
scrollAlignment | enum | The alignment of the highlighted item when scrolling. Default: 'nearest' |
loop | boolean | Whether or not the combobox menu should loop through items. Default: false |
items | array | Optionally provide an array of objects representing the items in the select for autofill capabilities. Only applicable to combobox's with type Default: undefined |
children | Snippet | The children content to render. Default: undefined |
A button which toggles the combobox's open state.
Property | Type | Description |
---|---|---|
ref $bindable | HTMLButtonElement | The underlying DOM element being rendered. You can bind to this to get a reference to the element. Default: undefined |
children | Snippet | The children content to render. Default: undefined |
child | Snippet | Use render delegation to render your own element. See Child Snippet docs for more information. Default: undefined |
Data Attribute | Value | Description |
---|---|---|
data-state | enum | The combobox's open state. |
data-disabled | '' | Present when the combobox is disabled. |
data-combobox-trigger | '' | Present on the trigger element. |
The element which contains the combobox's items.
Property | Type | Description |
---|---|---|
side | enum | The preferred side of the anchor to render the floating element against when open. Will be reversed when collisions occur. Default: bottom |
sideOffset | number | The distance in pixels from the anchor to the floating element. Default: 0 |
align | enum | The preferred alignment of the anchor to render the floating element against when open. This may change when collisions occur. Default: start |
alignOffset | number | The distance in pixels from the anchor to the floating element. Default: 0 |
arrowPadding | number | The amount in pixels of virtual padding around the viewport edges to check for overflow which will cause a collision. Default: 0 |
avoidCollisions | boolean | When Default: true |
collisionBoundary | union | A boundary element or array of elements to check for collisions against. Default: undefined |
collisionPadding | union | The amount in pixels of virtual padding around the viewport edges to check for overflow which will cause a collision. Default: 0 |
sticky | enum | The sticky behavior on the align axis. Default: partial |
hideWhenDetached | boolean | When Default: true |
updatePositionStrategy | enum | The strategy to use when updating the position of the content. When Default: optimized |
strategy | enum | The positioning strategy to use for the floating element. When Default: fixed |
preventScroll | boolean | When Default: false |
customAnchor | union | Use an element other than the trigger to anchor the content to. If provided, the content will be anchored to the provided element instead of the trigger. Default: null |
onEscapeKeydown | function | Callback fired when an escape keydown event occurs in the floating content. You can call Default: undefined |
escapeKeydownBehavior | enum | The behavior to use when an escape keydown event occurs in the floating content. Default: close |
onInteractOutside | function | Callback fired when an outside interaction event occurs, which is a Default: undefined |
onFocusOutside | function | Callback fired when focus leaves the dismissible layer. You can call Default: undefined |
interactOutsideBehavior | enum | The behavior to use when an interaction occurs outside of the floating content. Default: close |
onCloseAutoFocus | function | Event handler called when auto-focusing the content as it is closed. Can be prevented. Default: undefined |
preventOverflowTextSelection | boolean | When Default: true |
dir | enum | The reading direction of the app. Default: ltr |
loop | boolean | Whether or not the combobox should loop through items when reaching the end. Default: false |
forceMount | boolean | Whether or not to forcefully mount the content. This is useful if you want to use Svelte transitions or another animation library for the content. Default: false |
ref $bindable | HTMLDivElement | The underlying DOM element being rendered. You can bind to this to get a reference to the element. Default: undefined |
children | Snippet | The children content to render. Default: undefined |
child | Snippet | Use render delegation to render your own element. See Child Snippet docs for more information. Default: undefined |
Data Attribute | Value | Description |
---|---|---|
data-state | enum | The combobox's open state. |
data-combobox-content | '' | Present on the content element. |
CSS Variable | Description |
---|---|
--bits-combobox-content-transform-origin | The transform origin of the combobox content element. |
--bits-combobox-content-available-width | The available width of the combobox content element. |
--bits-combobox-content-available-height | The available height of the combobox content element. |
--bits-combobox-anchor-width | The width of the combobox trigger element. |
--bits-combobox-anchor-height | The height of the combobox trigger element. |
The element which contains the combobox's items. (Static/No Floating UI)
Property | Type | Description |
---|---|---|
onEscapeKeydown | function | Callback fired when an escape keydown event occurs in the floating content. You can call Default: undefined |
escapeKeydownBehavior | enum | The behavior to use when an escape keydown event occurs in the floating content. Default: close |
onInteractOutside | function | Callback fired when an outside interaction event occurs, which is a Default: undefined |
onFocusOutside | function | Callback fired when focus leaves the dismissible layer. You can call Default: undefined |
interactOutsideBehavior | enum | The behavior to use when an interaction occurs outside of the floating content. Default: close |
onOpenAutoFocus | function | Event handler called when auto-focusing the content as it is opened. Can be prevented. Default: undefined |
onCloseAutoFocus | function | Event handler called when auto-focusing the content as it is closed. Can be prevented. Default: undefined |
trapFocus | boolean | Whether or not to trap the focus within the content when open. Default: true |
preventScroll | boolean | When Default: true |
preventOverflowTextSelection | boolean | When Default: true |
dir | enum | The reading direction of the app. Default: ltr |
loop | boolean | Whether or not the combobox should loop through items when reaching the end. Default: false |
forceMount | boolean | Whether or not to forcefully mount the content. This is useful if you want to use Svelte transitions or another animation library for the content. Default: false |
ref $bindable | HTMLDivElement | The underlying DOM element being rendered. You can bind to this to get a reference to the element. Default: undefined |
children | Snippet | The children content to render. Default: undefined |
child | Snippet | Use render delegation to render your own element. See Child Snippet docs for more information. Default: undefined |
Data Attribute | Value | Description |
---|---|---|
data-state | enum | The combobox's open state. |
data-combobox-content | '' | Present on the content element. |
A combobox item, which must be a child of the Combobox.Content
component.
Property | Type | Description |
---|---|---|
value required | string | The value of the item. Default: undefined |
label | string | The label of the item, which is what the list will be filtered by. Default: undefined |
disabled | boolean | Whether or not the combobox item is disabled. This will prevent interaction/selection. Default: false |
onHighlight | function | A callback that is fired when the item is highlighted. Default: undefined |
onUnhighlight | function | A callback that is fired when the item is unhighlighted. Default: undefined |
ref $bindable | HTMLDivElement | The underlying DOM element being rendered. You can bind to this to get a reference to the element. Default: undefined |
children | Snippet | The children content to render. Default: undefined |
child | Snippet | Use render delegation to render your own element. See Child Snippet docs for more information. Default: undefined |
Data Attribute | Value | Description |
---|---|---|
data-value | string | The value of the combobox item. |
data-label | string | The label of the combobox item. |
data-disabled | '' | Present when the item is disabled. |
data-highlighted | '' | Present when the item is highlighted, which is either via keyboard navigation of the menu or hover. |
data-selected | '' | Present when the item is selected. |
data-combobox-item | '' | Present on the item element. |
A representation of the combobox input element, which is typically displayed in the content.
Property | Type | Description |
---|---|---|
defaultValue | string | The default value of the input. This is not a reactive prop and is only used to populate the input when the combobox is first mounted if there is already a value set. Default: undefined |
ref $bindable | HTMLInputElement | The underlying DOM element being rendered. You can bind to this to get a reference to the element. Default: undefined |
children | Snippet | The children content to render. Default: undefined |
child | Snippet | Use render delegation to render your own element. See Child Snippet docs for more information. Default: undefined |
Data Attribute | Value | Description |
---|---|---|
data-state | enum | The combobox's open state. |
data-disabled | '' | Present when the combobox is disabled. |
data-combobox-input | '' | Present on the input element. |
A heading for the parent combobox group. This is used to describe a group of related combobox items.
Property | Type | Description |
---|---|---|
ref $bindable | HTMLDivElement | The underlying DOM element being rendered. You can bind to this to get a reference to the element. Default: undefined |
children | Snippet | The children content to render. Default: undefined |
child | Snippet | Use render delegation to render your own element. See Child Snippet docs for more information. Default: undefined |
Data Attribute | Value | Description |
---|---|---|
data-combobox-group-heading | '' | Present on the group heading element. |
An optional arrow element which points to the content when open.
Property | Type | Description |
---|---|---|
width | number | The width of the arrow in pixels. Default: 8 |
height | number | The height of the arrow in pixels. Default: 8 |
ref $bindable | HTMLDivElement | The underlying DOM element being rendered. You can bind to this to get a reference to the element. Default: undefined |
children | Snippet | The children content to render. Default: undefined |
child | Snippet | Use render delegation to render your own element. See Child Snippet docs for more information. Default: undefined |
Data Attribute | Value | Description |
---|---|---|
data-arrow | '' | Present on the arrow element. |