Components / Library version 3.20.0

Select

This component provides a dropdown list of options, similar to the HTML select element. It displays the selected option(s) when the dropdown is closed.

Several variants are available. Single Select (the default), multiselect, which has an optional "Select All" button, and a search field to filter the options (which can be used with both single and multiselect).

NB: If you want to implement a dropdown where activating an item triggers an action, please see the Action Menu's selector variant.

Technical overview

The component should be used exclusively with the wm-option component, which represent the options.

To use the component, listen to the wmSelectChanged event on wm-select. event.detail contains additional information, like the reference to the option the user clicked and the list of selected options. See the Events tabs for more information.

Properties Examples Events Accessibility Notes

* Required property

label *
string
A description for the dropdown. Required even if the label-position is set to none (for accessibility reasons).
label-position
top | left | none
Defaults to top. Set this property to none if no label should be displayed.
max-height
string
Overwrites the default max-height value for the options list. It takes any valid CSS value. Default is 12.5rem.
required-field
boolean
Renders an asterisk indicating that the field is required.
invalid
boolean
Changes the input border color to red.
error-message
string
The message to display if the user input fails a validation performed outside of the component. The component is in error state while this property is set.
disabled
boolean
Disables the component.
multiple
boolean
Allows for the selection of multiple options.
select-all
boolean
Adds a "Select All" button above the options. The button text is "Deselect All" when all options are selected.
placeholder
string
For the multiple variant, sets the placeholder text when no options are selected. Defaults to "Make a selection". To use a placeholder with the single select, see the Notes tab.
search-placeholder
string
For the search variant, sets the placeholder text that appears in the search field. Defaults to "Search".
all-selected-message
string
For the multiple variant, sets the text to display when all options are selected and some are overflowing. Defaults to "All selected".

For the properties of the children, see option.

Usage in HTML

Edit the code below to see changes reflected in the example above.

Javascript Sample

Example code for functionality.

Usage in Elm

Code generated from HTML.
wmSelectBlurred
Emitted when the field blurs. Listen for this event to run validation functions. Do not use the standard onBlur event, which will not have the desired behavior.
wmSelectChanged
Emitted when the selected option(s) change(s). event.detail is an object containing two keys: optionChanged is the option which the user selected, and selectedOptions is an array of all the selected options (relevant with multiselect only).

Deprecated properties

change
Deprecated in favor of wmSelectChanged.
wmComponentBlurred
Deprecated in favor of wmSelectBlurred.

Keyboard Support

Button

Key Function
Space Enter Opens dropdown and focuses the selected option. If no option is selected, the first option is selected by default.
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.

Dropdown Listbox

Key Function
Space
  • Selects the option. In the multiple variant, toggles the option.
  • Closes the menu and sets focus on the button. In the multiple variant, the menu stays open.
Enter
  • Selects the option. In the multiple variant, toggles the option.
  • Closes the menu.
  • Sets focus on the button.
Escape
  • Closes the dropdown.
  • Sets focus to the button.
Up Arrow
  • Moves focus to the previous option.
  • If focus is on the first option, moves focus to the last option.
Down Arrow
  • Moves focus to the next option.
  • If focus is on the last option, moves focus to the first option.
Home Moves focus to the first option.
End Moves focus to the last option.
A-Z
  • Moves focus to the next option with a label that starts with the typed character if such an option exists.
  • Otherwise, focus does not move.

Usage & API

  • Only use wm-option's selected attribute for the initial selection. If you need to change the selected options, re-render the component.
  • The Select with Search variants are intended to be used with 50 or fewer options. Any more present usability and potential performance issues. Designs that call for a Select with Search with more than 50 options should consider an alternate pattern.

Single Select's "placeholder"

Single Select doesn't have a placeholder, but most of the time this UX pattern requires a "special" first option, otherwise we have no way to know whether the user selected the first option or didn't make a selection at all. You may use the first option as a null value to resolve this issue. In this case, for accessibility and consistency reasons, the language should be limited to one of the following:

  • None
  • Select an option
  • --

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-menuitem>, <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.