Menu

A menu of choices or commands
New Tab New Window History Downloads Bookmarks Zoom Settings
Demo: A Menu attached to a MenuButton

Overview

Menu is used to present a set of choices or commands as a menu. Menu holds the contents of a menu popup — the choices or commands in the menu — and is not the top-level UI element that invokes the menu. For that, see MenuButton, DropdownList, or the more fundamental PopupSource.

Menu can be used with MenuItem and MenuSeparator children, but those simply provide standard appearances. You can use any type of child element inside a Menu. For example, this DropdownList example uses custom elements as the children of the Menu:

Black Blue Green Orange Purple Red White Yellow
Demo: DropdownList showing custom elements as menu choices

Usage

import Menu from 'elix/define/Menu.js';
const Menu = new Menu(); // or
const Menu = document.createElement('elix-menu');

In HTML:

<elix-menu>
  <elix-menu-item>New</elix-menu-item>
  <elix-menu-item>Open</elix-menu-item>
  <elix-menu-separator></elix-menu-separator>
  <elix-menu-item>Save</elix-menu-item>
  <elix-menu-separator></elix-menu-separator>
  <elix-menu-item>Close</elix-menu-item>
</elix-menu>

Keyboard behavior

A Menu is similar to a ListBox in behavior, particularly keyboard behavior. However, one way in which menus are different from lists is that a list will typically present itself as a single focusable item; the list items themselves are not independently focusable. In contrast, a Menu presents each of its children as a separately focusable item. This is done in order to ensure that assistive technologies such as screen readers interpret the menu items correctly.

See also

API

Class hierarchy:

This element is used as a shadow part in DropdownList and MenuButton.

closestAvailableItemIndex(state, options) method

Look for an item which is available in the given state..

The options parameter can accept options for:

  • direction: 1 to move forward, -1 to move backward
  • index: the index to start at, defaults to state.currentIndex
  • wrap: whether to wrap around the ends of the items array, defaults to state.cursorOperationsWrap.

If an available item was found, this returns its index. If no item was found, this returns -1.

Parameters:

  • state: PlainObject
  • options: PlainObject

Returns: number

Defined by ItemsCursorMixin

contentSlot property

See contentSlot.

Defined by SlotContentMixin

currentIndex property

The index of the current item, or -1 if no item is current.

Type: number

Defined by CursorAPIMixin

currentindexchanged event

Raised when the currentIndex property changes.

Defined by CursorAPIMixin

currentItem property

The current item, or null if no item is current.

Type: Element

Defined by CursorAPIMixin

currentItemRequired property

True if the list should always have a current item (if it has items).

Type: boolean

Default: false

Defined by CursorAPIMixin

cursorOperationsWrap property

True if cursor operations wrap from last to first, and vice versa.

Type: boolean

Default: false

Defined by CursorAPIMixin

defaultState property

The default state for the component. This can be extended by mixins and classes to provide additional default state.

Type: PlainObject

Defined by ReactiveMixin

delegatesFocus property

Returns true if the component is delegating its focus.

A component using DelegateFocusMixin will always have this property be true unless a class takes measures to override it.

Type: boolean

Default: true

Defined by DelegateFocusMixin

flashCurrentItem() method

Flash the current item.

By default, this uses a heuristic to guess whether the menu was closed by a keyboard or mouse (on desktop). If so, the menu flashes the current item off then back on, emulating the menu item selection effect in macOS. Otherwise, it does nothing.

getItemText(item) method

Extract the text from the given item.

The default implementation returns an item's aria-label, alt attribute, or its textContent, in that order. You can override this to return the text that should be used.

Parameters:

  • item: Element

Returns: string

Defined by ItemsTextMixin

goDown() method

Interprets goDown to mean "move to the next item".

Defined by DirectionCursorMixin

goEnd() method

Interprets goEnd to mean "move to the last item".

Defined by DirectionCursorMixin

goFirst() method

Moves to the first item in the list.

Returns: Boolean True if the current item changed, false if not.

Defined by CursorAPIMixin

goLast() method

Move to the last item in the list.

Returns: Boolean True if the current item changed

Defined by CursorAPIMixin

goLeft() method

Interprets goLeft to mean "move to the previous item".

If the element has a rightToLeft property and it is true, then this moves to the next item.

Defined by DirectionCursorMixin

goNext() method

Move to the next item in the list.

If the list has no current item, the first item will become current.

Returns: Boolean True if the current item changed

Defined by CursorAPIMixin

goPrevious() method

Moves to the previous item in the list.

If the list has no current item, the last item will become current.

Returns: Boolean True if the current item changed

Defined by CursorAPIMixin

goRight() method

Interprets goRight to mean "move to the next item".

If the element has a rightToLeft property and it is true, then this moves to the previous item.

Defined by DirectionCursorMixin

goStart() method

Interprets goStart to mean "move to the first item".

Defined by DirectionCursorMixin

goToItemWithPrefix(prefix) method

Go to the first item whose text content begins with the given prefix.

Parameters:

  • prefix: stringThe prefix string to search for

Returns: boolean

Defined by KeyboardPrefixCursorMixin

goUp() method

Interprets goUp to mean "move to the previous item".

Defined by DirectionCursorMixin

ids property

A convenient shortcut for looking up an element by ID in the component's Shadow DOM subtree.

Example: if component's template contains a shadow element <button id="foo">, you can use the reference this[ids].foo to obtain the corresponding button in the component instance's shadow tree. The ids property is simply a shorthand for getElementById, so this[ids].foo is the same as this[shadowRoot].getElementById('foo').

Type: object

Defined by ShadowTemplateMixin

[internal.goFirst]() method

Move to the first item in the set.

Returns: Boolean True if the current item changed, false if not.

Defined by ItemsCursorMixin

[internal.goLast]() method

Move to the last item in the set.

Returns: Boolean True if the current item changed, false if not.

Defined by ItemsCursorMixin

[internal.goNext]() method

Move to the next item in the set.

If no item is current, move to the first item.

Returns: Boolean True if the current item changed, false if not.

Defined by ItemsCursorMixin

[internal.goPrevious]() method

Move to the previous item in the set.

If no item is current, move to the last item.

Returns: Boolean True if the current item changed, false if not.

Defined by ItemsCursorMixin

items property

The current set of items drawn from the element's current state.

Type: Array.

Defined by ItemsAPIMixin

itemschange event

Raised when the items property changes.

Defined by ItemsAPIMixin

keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin

pageDown() method

Scroll down one page.

Defined by KeyboardPagedCursorMixin

pageUp() method

Scroll up one page.

Defined by KeyboardPagedCursorMixin

render(changed) method

Render the indicated changes in state to the DOM.

The default implementation of this method does nothing. Override this method in your component to update your component's host element and any shadow elements to reflect the component's new state. See the rendering example.

Be sure to call super in your method implementation so that your component's base classes and mixins have a chance to perform their own render work.

Parameters:

  • changed: ChangedFlagsdictionary of flags indicating which state members have changed since the last render

Defined by ReactiveMixin

renderChanges() method

Render any pending component changes to the DOM.

This method does nothing if the state has not changed since the last render call.

ReactiveMixin will invoke this method following a setState call; you should not need to invoke this method yourself.

This method invokes the internal render method, then invokes the rendered method.

Defined by ReactiveMixin

rendered(changed) method

Perform any work that must happen after state changes have been rendered to the DOM.

The default implementation of this method does nothing. Override this method in your component to perform work that requires the component to be fully rendered, such as setting focus on a shadow element or inspecting the computed style of an element. If such work should result in a change in component state, you can safely call setState during the rendered method.

Be sure to call super in your method implementation so that your component's base classes and mixins have a chance to perform their own post-render work.

Parameters:

  • changed: ChangedFlags

Defined by ReactiveMixin

scrollCurrentItemIntoView() method

Scroll the current item completely into view, minimizing the degree of scrolling performed.

Blink has a scrollIntoViewIfNeeded() function that does something similar, but unfortunately it's non-standard, and in any event often ends up scrolling more than is absolutely necessary.

This scrolls the containing element defined by the scrollTarget property. By default, it will scroll the element itself.

Defined by CursorInViewMixin

scrollTarget property

The element that should be scrolled to get the selected item into view.

By default, this uses the defaultScrollTarget helper to find the most likely candidate for scrolling. You can override this property to directly identify which element should be scrolled.

See also scrollTarget.

Defined by CursorInViewMixin

selectedIndex property

The index of the selected item, or -1 if no item is selected.

Type: number

Defined by SingleSelectAPIMixin

selectedindexchange event

Raised when the selectedIndex property changes.

Defined by SingleSelectAPIMixin

selectedItem property

The selected item, or null if no item is selected.

Type: Element

Defined by SingleSelectAPIMixin

setState(changes) method

Update the component's state by merging the specified changes on top of the existing state. If the component is connected to the document, and the new state has changed, this returns a promise to asynchronously render the component. Otherwise, this returns a resolved promise.

Parameters:

  • changes: PlainObjectthe changes to apply to the element's state

Returns: Promise - resolves when the new state has been rendered

Defined by ReactiveMixin

state property

The component's current state.

The returned state object is immutable. To update it, invoke internal.setState.

It's extremely useful to be able to inspect component state while debugging. If you append ?elixdebug=true to a page's URL, then ReactiveMixin will conditionally expose a public state property that returns the component's state. You can then access the state in your browser's debug console.

Type: PlainObject

Defined by ReactiveMixin

stateEffects(state, changed) method

Ask the component whether a state with a set of recently-changed fields implies that additional second-order changes should be applied to that state to make it consistent.

This method is invoked during a call to internal.setState to give all of a component's mixins and classes a chance to respond to changes in state. If one mixin/class updates state that it controls, another mixin/class may want to respond by updating some other state member that it controls.

This method should return a dictionary of changes that should be applied to the state. If the dictionary object is not empty, the internal.setState will apply the changes to the state, and invoke this stateEffects method again to determine whether there are any third-order effects that should be applied. This process repeats until all mixins/classes report that they have no additional changes to make.

See an example of how ReactiveMixin invokes the stateEffects to ensure state consistency.

Parameters:

  • state: PlainObjecta proposal for a new state
  • changed: ChangedFlagsthe set of fields changed in this latest proposal for the new state

Returns: PlainObject

Defined by ReactiveMixin