@material/icon-toggle

MDC Icon Toggle

MDC Icon Toggle provides a material design icon toggle button. It is fully accessible, and is designed to work with any icon set.

Installation

npm install --save @material/icon-toggle

Usage

In order to use MDC Icon Toggle, you will need to import an icon set, such as Material Icons or Font Awesome.

<i class="mdc-icon-toggle material-icons" role="button" aria-pressed="false"
   aria-label="Add to favorites" tabindex="0"
   data-toggle-on='{"label": "Remove from favorites", "content": "favorite"}'
   data-toggle-off='{"label": "Add to favorites", "content": "favorite_border"}'>
  favorite_border
</i>

Then in JS

import {MDCIconToggle} from 'mdc-icon-toggle';

MDCIconToggle.attachTo(document.querySelector('.mdc-icon-toggle'));

Note that you can access MDCIconToggle via CommonJS/AMD using the default property of the required object, as well as globally via mdc.IconToggle.

Also note that you may omit the initial aria-label attribute and favorite_border content since they will be added by the component. However, we recommend adding to prevent an initial flash of un-styled content.

Using with Font Awesome and similar libraries

Font Awesome - as well as other popular icon font libraries - use pseudo-elements in order to provide the icon, via the content property. However, MDC-Web uses pseudo-elements for ripple styles. In order to get around this, you can nest the icon itself inside the icon toggle.

<span class="mdc-icon-toggle" role="button" aria-pressed="false"
      aria-label="Star this item" tabindex="0"
      data-icon-inner-selector=".fa"
      data-toggle-on='{"cssClass": "fa-star", "label": "Unstar this item"}'
      data-toggle-off='{"cssClass": "fa-star-o", "label": "Star this item"}'>
  <i class="fa fa-star-o" aria-hidden="true"></i>
</span>

data-icon-inner-selector tells MDCIconToggle to look for an element within itself that matches that selector, and treat it as the element containing the icon. Also note the aria-hidden attribute on the icon. This is important to ensure that screen readers produce the correct output when reading this element.

Configuring the icon toggle states

Note the use of data-toggle-on and data-toggle-off in the above examples. When an MDCIconToggle instance is toggled, it looks at this data to determine how to update the element. This is what allows MDCIconToggle to be so flexible. The data-toggle-on configuration will be used when the is MDCIconToggle is toggled on, and vice versa for data-toggle-off. Both data attributes are encoded as JSON and can contain the following properties:

Property	Description
label	The value to apply to the element's "aria-label" attribute.
content	The text content to set on the element. Note that if an inner icon is used, the text content will be set on that element instead.
cssClass	A css class to apply to the icon element for the given toggle state. The same rules regarding inner icon elements described for content apply here as well.

Disabled icon toggles

<i class="material-icon mdc-icon-toggle mdc-icon-toggle--disabled"
   role="button" tabindex="-1" aria-pressed="false" aria-disabled="true"
   data-toggle-on='{"content": "favorite"}' data-toggle-off='{"content": "favorite_border"}'></i>

Theming

mdc-icon-toggle ships with two css classes, mdc-icon-toggle--primary and mdc-icon-toggle--accent that allow you to color mdc-icon-toggle based on your primary and accent colors, respectively.

Listening for change events

MDCIconToggle emits an MDCIconToggle:change custom event when the value of the icon toggle changes as a result of user input. This decision was made to align with how change events work for normal inputs. In addition, these events do not bubble and cannot be cancelled.

The custom event's detail object contains a property isOn denoting whether or not the component is toggled on.

const iconEl = document.querySelector('.mdc-icon-toggle');
const status = document.getElementById('status');
iconEl.addEventListener('MDCIconToggle:change', ({detail}) => {
  status.textContent = `Icon Toggle is ${detail.isOn ? 'on' : 'off'}`;
});

Refreshing the toggle data via the vanilla component.

When the icon toggle is initialized, the data-toggle-on and data-toggle-off attributes are cached to prevent redundant JSON parsing whenever the element is interacted with. However, if you need to, you can call refreshToggleData():

iconToggle.refreshToggleData();

This simply forwards a call to the foundation's refreshToggleData() method, causing the data-toggle-* attributes to be re-parsed and updated.

This method is useful for frameworks that incrementally render DOM. If an icon toggle's data attributes change, the component needs a way to update itself. This is the reason why this method is exposed on the foundation, and simply proxied by the vanilla component.

MDCIconToggle API

Similar to regular DOM elements, the MDCIconToggle functionality is exposed through accessor methods.

MDCIconToggle.on

Boolean. Returns whether or not the icon toggle is currently toggled on. Setting this property will update the toggle state.

MDCIconToggle.disabled

Boolean. Returns whether or not the icon toggle is currently disabled. Setting this property will update the disabled state.

Using the Foundation Class

MDCIconToggle ships with an MDCIconToggleFoundation class that external frameworks and libraries can use to build their own MDCIconToggle components with minimal effort. As with all foundation classes, an adapter object must be provided. The adapter for icon toggles must provide the following functions, with correct signatures:

Method Signature	Description
addClass(className: string) => void	Adds a class to the root element, or the inner icon element.
removeClass(className: string) => void	Removes a class from the root element, or the inner icon element.
registerInteractionHandler(type: string, handler: EventListener) => void	Registers an event handler for an interaction event, such as click or keydown.
deregisterInteractionHandler(type: string, handler: EventListener) => void	Removes an event handler for an interaction event, such as click or keydown.
setText(text: string) => void	Sets the text content of the root element, or the inner icon element.
getTabIndex() => number	Returns the tab index of the root element.
setTabIndex(tabIndex: number) => void	Sets the tab index of the root element.
getAttr(name: string) => string	Returns the value of the attribute name on the root element. Can also return null, similar to getAttribute().
setAttr(name: string, value: string) => void	Sets the attribute name to value on the root element.
rmAttr(name: string) => void	Removes the attribute name on the root element.
notifyChange(evtData: {isOn: boolean}) => void	Broadcasts a change notification, passing along the evtData to the environment's event handling system. In our vanilla implementation, Custom Events are used for this.

Adapter implementer considerations

If you are writing your own adapter, one thing that needs to be considered is the use of data-icon-inner-selector. This is handled by us at the component level, which means our foundation is completely unaware of it. To that end, if your framework's Icon Toggle support inner icon elements, you must ensure that addClass, removeClass, and setText apply to the correct icon element.

Also note that ripples require their own foundation at the component level. Check out our vanilla implementation in index.js as a starting point.

Full foundation API

MDCIconToggleFoundation.refreshToggleData() => void

As described above, the data-toggle-* attributes are cached so as not to have to perform redundant parsing. If your framework performs incremental rendering, and these attributes change without re-rendering the component itself, you can call this method to re-parse the data attributes and keep the foundation updated.

MDCIconToggleFoundation.isOn() => boolean

Returns true if the foundation's state is toggled on, false otherwise.

MDCIconToggleFoundation.toggle(isOn: boolean = !this.isOn()) => void

Toggles the foundation's state, updating the component via the adapter methods. Defaults to the toggling the opposite of the current state if no argument given. If an argument is given, will toggle on if true, off if false.

MDCIconToggleFoundation.isDisabled() => boolean

Returns true if the foundation's state is disabled, false otherwise.

MDCIconToggleFoundation.toggle(isDisabled: boolean) => void

Enables / disables the foundation's state, updating the component via the adapter methods.

MDCIconToggleFoundation.isKeyboardActivated() => boolean

Returns true if the foundation is currently activated by a keyboard event, false otherwise. Useful for MDCRippleFoundation's isSurfaceActive() adapter method.