Command
A command menu component that can be used to search, filter, and select items.
Overview
The Command component, also known as a command menu, is designed to provide users with a quick and efficient way to search, filter, and select items within an application. It combines the functionality of a search input with a dynamic, filterable list of commands or options, making it ideal for applications that require fast navigation or action execution.
Key Features
- Dynamic Filtering: As users type in the input field, the list of commands or items is instantly filtered and sorted based on an (overridable) scoring algorithm.
- Keyboard Navigation: Full support for keyboard interactions, allowing users to quickly navigate and select items without using a mouse.
- Grouped Commands: Ability to organize commands into logical groups, enhancing readability and organization.
- Empty and Loading States: Built-in components to handle scenarios where no results are found or when results are being loaded.
- Accessibility: Designed with ARIA attributes and keyboard interactions to ensure screen reader compatibility and accessibility standards.
Architecture
The Command component is composed of several sub-components, each with a specific role:
- Root: The main container that manages the overall state and context of the command menu.
- Input: The text input field where users can type to search or filter commands.
- List: The container for the list of commands or items.
- Viewport: The visible area of the command list, which applies CSS variables to handle dynamic resizing/animations based on the height of the list.
- Empty: A component to display when no results are found.
- Loading: A component to display while results are being fetched or processed.
- Group: A container for a group of items within the command menu.
- GroupHeading: A header element to provide an accessible label for a group of items.
- GroupItems: A container for the items within a group.
- Item: Individual selectable command or item.
- LinkItem: A variant of
Command.Item
specifically for link-based actions. - Separator: A visual separator to divide different sections of the command list.
Structure
Here's an overview of how the Command component is structured in code:
Managing Value State
Bits UI offers several approaches to manage and synchronize the Command'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 theCommand.Root
component. - Provide a
value
prop toCommand.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 value change 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.
In a Modal
You can combine the Command
component with the Dialog
component to display the command menu within a modal.
Filtering
Custom Filter
By default, the Command
component uses a scoring algorithm to determine how the items should be sorted/filtered. You can provide a custom filter function to override this behavior.
The function should return a number between 0
and 1
, with 1
being a perfect match, and 0
being no match, resulting in the item being hidden entirely.
The following example shows how you might implement a strict substring match filter:
Disable Filtering
You can disable filtering by setting the shouldFilter
prop to false
.
This is useful when you have a lot of custom logic, need to fetch items asynchronously, or just want to handle filtering yourself. You'll be responsible for iterating over the items and determining which ones should be shown.
Item Selection
You can use the onSelect
prop to handle the selection of items.
Links
If you want one of the items to get all the benefits of a link (prefetching, etc.), you should use the Command.LinkItem
component instead of the Command.Item
component. The only difference is that the Command.LinkItem
component will render an a
element instead of a div
element.
API Reference
The main container that manages the overall state and context of the component.
Property | Type | Description |
---|---|---|
value $bindable | string | The value of the command. Default: undefined |
onValueChange | function | A callback that is fired when the command value changes. Default: undefined |
controlledValue | boolean | Whether or not the value is controlled or not. If Default: false |
label | string | An accessible label for the command menu. This is not visible and is only used for screen readers. Default: undefined |
filter | function | A custom filter function used to filter items. This function should return a number between Default: undefined |
shouldFilter | boolean | Whether or not the command menu should filter items. This is useful when you want to apply custom filtering logic outside of the Command component. Default: true |
loop | boolean | Whether or not the command menu should loop through items when navigating with the keyboard. Default: false |
disablePointerSelection | boolean | Set this to true to prevent items from being selected when the users pointer moves over them. Default: false |
vimBindings | boolean | Whether VIM bindings should be enabled or not, which allow the user to navigate using ctrl+n/j/p/k Default: true |
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-command-root | '' | Present on the root element. |
The text input field where users can type to search or filter commands.
Property | Type | Description |
---|---|---|
value $bindable | string | The value of the search query. This is used to filter items and to search for items. 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-command-input | '' | Present on the input element. |
The container for the viewport, items, and other elements of the command menu.
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-command-list | '' | Present on the list element. |
CSS Variable | Description |
---|---|
--bits-command-list-height | The height of the command list element, which is computed by the |
The visible area of the command list, which applies CSS variables to handle dynamic resizing/animations based on the height of the list.
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-command-viewport | '' | Present on the viewport element. |
A container for a group of items within the command menu.
Property | Type | Description |
---|---|---|
value | string | If a Default: undefined |
forceMount | boolean | Whether or not the group should always be mounted to the DOM, regardless of the internal filtering logic 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-command-group | '' | Present on the group element. |
A heading element to provide an accessible label for a group of 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-command-group-heading | '' | Present on the group heading element. |
The container for the items within a group.
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-command-group-items | '' | Present on the group items element. |
Represents a single item within the command menu. If you wish to render an anchor element to link to a page, use the Command.LinkItem
component.
Property | Type | Description |
---|---|---|
value required | string | The value of the item. Default: undefined |
keywords | string[] | An array of additional keywords or aliases that will be used to filter the item. Default: undefined |
forceMount | boolean | Whether or not the item should always be mounted to the DOM, regardless of the internal filtering logic Default: false |
onSelect | function | A callback that is fired when the item is selected. Default: undefined |
disabled | boolean | Whether or not the combobox item is disabled. This will prevent interaction/selection. 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-disabled | '' | Present when the item is disabled. |
data-selected | '' | Present when the item is selected. |
data-command-item | '' | Present on the item element. |
Similar to the Command.Item
component, but renders an anchor element to take advantage of preloading before navigation.
Property | Type | Description |
---|---|---|
value required | string | The value of the item. Default: undefined |
keywords | string[] | An array of additional keywords or aliases that will be used to filter the item. Default: undefined |
forceMount | boolean | Whether or not the item should always be mounted to the DOM, regardless of the internal filtering logic Default: false |
onSelect | function | A callback that is fired when the item is selected. Default: undefined |
disabled | boolean | Whether or not the combobox item is disabled. This will prevent interaction/selection. 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-disabled | '' | Present when the item is disabled. |
data-selected | '' | Present when the item is selected. |
data-command-item | '' | Present on the item element. |
A component to display when no results are found.
Property | Type | Description |
---|---|---|
forceMount | boolean | Whether or not to forcefully mount the empty state, regardless of the internal filtering logic. Useful when you want to handle filtering yourself. 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-command-empty | '' | Present on the empty element. |
A component to display while results are being fetched or processed.
Property | Type | Description |
---|---|---|
progress | number | The progress of the loading state. Default: 0 |
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-command-loading | '' | Present on the loading element. |
A visual separator to divide different sections of the command list. Visible when the search query is empty or the forceMount
prop is true
.
Property | Type | Description |
---|---|---|
forceMount | boolean | Whether or not the separator should always be mounted to the DOM, regardless of the internal filtering logic 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-command-separator | '' | Present on the separator element. |