A button that invokes a menu
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Demo: A MenuButton can be used to provide access to less frequently-used commands


MenuButton is a button that invokes a menu. By default, clicking the button invokes an instance of Menu. You can customize that by setting the menuTag property.

MenuButton is a rather general base class for creating buttons that invoke menus, and as such does not itself do any work in response to selections the user may make from the menu. For a version of MenuButton optimized for selecting a single item from a list of choices, see DropdownList.

Mouse support

MenuButton lets a user select a command with the mouse in two ways:

  1. Select a menu item with two separate clicks. The first click opens the menu; the second picks a command from the menu. To cancel the operation, the user can click outside the menu.

  2. Select a menu item in a single drag operation. The user mouses down on the menu button, which opens the menu underneath the mouse. Keeping the mouse button down, the user drags into the menu. The menu tracks the selection under their mouse. The user releases the mouse to select a command. To cancel the operation, the user can move the mouse off the menu and release the mouse. (The operation will also be canceled if the user releases the mouse over a disabled menu item or menu separator.) This behavior is provided via PopupDragSelectMixin and PopupListMixin.

Keyboard support

When the MenuButton has focus and the menu is closed, the user can open the menu by pressing Space or the Up or Down arrow keys.

When the menu is open, the user can move the selection with the arrow keys, Home, End, Page Up, or Page Down. They can also type the letters that begin a command's text. The user can select a command and close the menu by pressing Enter, or dismiss the menu by pressing Esc.

By default, MenuButton displays the items in a Menu which, when open, will give the keyboard focus to the currently-selected item.

See also

Shows a single choice made from a pop-up list of choices
A menu of choices or commands


Class hierarchy:

The element defines the following shadow parts:

  • menu: the menu shown in the popup, default type is Menu
  • popup: the popup element, default type is Popup
  • source: the element used as the reference point for positioning the popup, generally the element that invokes the popup, default type is button element

booleanAttributeValue(name, value) static method

Given a string value for a named boolean attribute, return true if the value is either: a) the empty string, or b) a case-insensitive match for the name.

This is native HTML behavior; see the MDN documentation on boolean attributes for the reasoning.

Given a null value, this return false. Given a boolean value, this return the value as is.


  • name: string
  • value: string|boolean|null

Defined by AttributeMarshallingMixin

close(closeResult) method

Close the component (if not already closed).

Some components like AlertDialog want to indicate why or how they were closed. To support such scenarios, you can supply a value to the optional closeResult parameter. This closeResult will be made available in the whenClosed promise and the state.closeResult member.


  • closeResult: objectan indication of how or why the element closed

Defined by OpenCloseMixin

close event

Raised when the component closes.

Defined by OpenCloseMixin

closed property

True if the element is currently closed.

This read-only property is provided as a convenient inverse of opened.

Type: boolean

Defined by OpenCloseMixin

closeFinished property

True if the element has completely closed.

For components not using asynchronous open/close effects, this property returns the same value as the closed property. For elements that have a true value of state.openCloseEffects (e.g., elements using TransitionEffectMixin), this property returns true only if state.effect is "close" and state.effectPhase is "after".

Type: boolean

Defined by OpenCloseMixin

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

disabled property

True if the component is disabled, false (the default) if not.

The value of this property will be reflected to the disabled attribute so that it can be referenced in CSS. Note that this non-native implementation of the disabled attribute will not trigger the :disabled CSS pseudo-class, so your style rules will have to reference the presence or absence of the disabled attribute. That is, instead of writing

my-component:disabled { ... }

write this instead

my-component[disabled] { ... }

Like the native disabled attribute, this attribute is boolean. That means that it's existence in markup sets the attribute, even if set to an empty string or a string like "false".

Type: boolean

Default: false

Defined by DisabledMixin

disabledchange event

Raised when the disabled property changes.

Defined by DisabledMixin

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

keydown() method

See the symbols documentation for details.

Defined by KeyboardMixin

menuPartType property

The class or tag used to define the menu part – the element presenting the menu items and handling navigation between them.

Type: (component class constructor)|HTMLTemplateElement|string

Default: Menu

open() method

Open the element (if not already opened).

Defined by OpenCloseMixin

open event

Raised when the component opens.

Defined by OpenCloseMixin

opened property

True if the element is currently opened.

This property can be set as a boolean attribute

Type: boolean

Default: false

Defined by OpenCloseMixin

openedchange event

Raised when the opened/closed state of the component changes.

Defined by OpenCloseMixin

popupAlign property

The alignment of the popup with respect to the source button.

  • bottom: popup and source are bottom-aligned
  • end: popup and source are aligned on the trailing edge according to the text direction
  • left: popup and source are left-aligned
  • right: popup and source are right-aligned
  • start: popup and source are aligned on the leading edge according to the text direction
  • stretch: both left and right edges are aligned
  • top: popup and source are top-aligned
     <p><span class="apiLabel">Type:</span> <code>'bottom'|'end'|'left'|'right'|'start'|'stretch'|'top'</code></p> <p><span class="apiLabel">Default:</span> <code>'start'</code></p>  <p> Defined by <a href="PopupSource">PopupSource</a> </p> 

popupDirection property

The preferred direction for the popup.

  • above: popup appears above the source
  • below: popup appears below the source
  • column-reverse: popup appears before the source in the block axis
  • column: popup appears after the source in the block axis
  • left: popup appears to the left of the source
  • right: popup appears to the right of the source
  • row-reverse: popup appears before the source in the inline axis
  • row: popup appears after the source in the inline axis
     <p><span class="apiLabel">Type:</span> <code>'above'|'below'|'column-reverse'|'column'|'left'|'right'|'row-reverse'|'row'</code></p> <p><span class="apiLabel">Default:</span> <code>'column'</code></p>  <p> Defined by <a href="PopupSource">PopupSource</a> </p> 

popupPartType property

The class or tag used to create the popup part – the element responsible for displaying the popup and handling overlay behavior.

Type: (component class constructor)|HTMLTemplateElement|string

Default: Popup

Defined by PopupSource

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.


  • 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.


  • changed: ChangedFlags

Defined by ReactiveMixin

selectCurrentItemAndClose() method

Highlight the current item (if one exists), then close the menu.

Defined by PopupListMixin

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.


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

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

Defined by ReactiveMixin

sourcePartType property

The class or tag used to create the source part - the button (or other element) the user can tap/click to invoke the popup.

Type: (component class constructor)|HTMLTemplateElement|string

Default: 'button'

Defined by PopupSource

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 method 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.


  • 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

toggle(opened) method

Toggle the open/close state of the element.


  • opened: booleantrue if the element should be opened, false if closed.

Defined by OpenCloseMixin

whenClosed() method

This method can be used as an alternative to listening to the "openedchange" event, particularly in situations where you want to only handle the next time the component is closed.

Returns: Promise A promise that resolves when the element has completely closed, including the completion of any asynchronous opening effect.

Defined by OpenCloseMixin