This component provides a dropdown list of options, similar to the HTML select element. By default only a single selection can be made, but a multiple variant is supported.
When closed, it displays the selected option. The first option is selected by default. It should have at least one option component as a child.
NB: If you want to implement a dropdown where selecting an
item doesn't change the text displayed when the dropdown is closed, please
see the Action Menu component
* Required property
** Required in certain cases
label-positionis set to
none(for accessibility reasons).
top | left | none
top. Set this property to
noneif no label should be displayed.
max-heightvalue for the options list. It takes any valid CSS value. Default is 12.5rem.
For the properties of the children, see option.
Usage in HTML
Edit the code below to see changes reflected in the example above.
Usage in Elm
Code generated from HTML.
Opens dropdown and focuses the selected option. If no option is
|Down Arrow||Opens dropdown and focuses option one down from the last option selected.|
|Up Arrow||Opens dropdown and focuses option one up from the first option selected.|
|Home||Moves focus to the first option.|
|End||Moves focus to the last option.|
This component has no minimum width. This might be necessary, in
particular to ensure that the
subinfotext doesn't overlap the option text.
- This component has no maximum width. It will take the width of its parent by default.
To trigger an action when an option is selected, attach a function to the
onClickattribute of the
wm-option. (This is accessible: the component emits a click when the user selects an option with the Enter key).
The version with an
input(search field) is not implemented at this point.
- Depending on context, screen readers may not announce the expanded state. This is normal behavior and does not constitutes an accessibility issue.
In a compound component like Select or Action Menu, child components are rendered in the parent's
slot element, part of its shadow DOM tree. Slots essentially serve as a placeholder for markup that you the developer define in the light DOM tree, like
<wm-option>, text content, or other child elements.
The browser distributes the child elements defined in the light DOM into the shadow DOM of the parent. The result is a flattened DOM tree—a merger of the the light DOM and the shadow DOM. This flattened tree is what you see in DevTools and what is rendered on the page.
With the standard implementation of the component, dynamically updating the child items will throw an error. Elm's efficient diffing of the DOM will register that only the child items have changed and try to update them, but the component has already been composed.
Rendering the component in a Keyed node and giving it a dynamic id will cause the entire component, rather than just the child items, to render anew, avoiding the error.