Reference Source

coral-spectrum/coral-component-anchorbutton/src/scripts/AnchorButton.js

/**
 * Copyright 2019 Adobe. All rights reserved.
 * This file is licensed to you under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under
 * the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
 * OF ANY KIND, either express or implied. See the License for the specific language
 * governing permissions and limitations under the License.
 */

import {BaseComponent} from '../../../coral-base-component';
import {BaseButton} from '../../../coral-base-button';
import {transform, commons} from '../../../coral-utils';

// Key code
const SPACE = 32;

/**
 @class Coral.AnchorButton
 @classdesc A Link component rendering as a button allowing us to style an anchor element that both looks and behaves
 like a button rather than a link. It can receive keyboard focus regardless of whether or not it has an <code>href</code>
 attribute, can be activated using either the <code>SPACE</code> key or the <code>ENTER</code> key, and is identified to
 assistive technology as a button element.
 @htmltag coral-anchorbutton
 @htmlbasetag a
 @extends {HTMLAnchorElement}
 @extends {BaseComponent}
 @extends {BaseButton}
 */
class AnchorButton extends BaseButton(BaseComponent(HTMLAnchorElement)) {
  /** @ignore */
  constructor() {
    super();

    // Events
    this._delegateEvents(commons.extend(this._events, {
      keydown: '_onKeyDown',
      keyup: '_onKeyUp'
    }));

    // cannot use the events hash because events on disabled items are not reported
    this.addEventListener('click', this._onDisabledClick.bind(this));
  }

  /**
   Disables the button from user interaction.

   @type {Boolean}
   @default false
   @htmlattribute disabled
   @htmlattributereflected
   */
  get disabled() {
    return this._disabled || false;
  }

  set disabled(value) {
    this._disabled = transform.booleanAttr(value);
    this._reflectAttribute('disabled', this._disabled);

    this.classList.toggle('is-disabled', this._disabled);
    this.setAttribute('tabindex', this._disabled ? '-1' : '0');
    this[this._disabled ? 'setAttribute' : 'removeAttribute']('aria-disabled', this._disabled);
  }

  /**
   Keyboard handling per the WAI-ARIA button widget design pattern:
   https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/ARIA_Techniques/Using_the_button_role

   @ignore
   */
  _onKeyDown(event) {
    if (event.keyCode === SPACE) {
      event.preventDefault();
      this.click();
      this.classList.add('is-selected');
    }
  }

  /** @ignore */
  _onKeyUp(event) {
    if (event.keyCode === SPACE) {
      event.preventDefault();
      this.classList.remove('is-selected');
    }
  }

  /** @ignore */
  _onDisabledClick(event) {
    if (this.disabled) {
      event.preventDefault();
    }
  }

  // Override content zone name
  get _contentZones() {
    return {'coral-anchorbutton-label': 'label'};
  }

  /** @ignore */
  static get observedAttributes() {
    return super.observedAttributes.concat(['disabled']);
  }

  /** @ignore */
  render() {
    super.render();

    // a11y
    this.setAttribute('role', 'button');
    if (!this.disabled) {
      // Force tabindex and aria-disabled attribute reflection
      this.setAttribute('tabindex', '0');
      this.removeAttribute('aria-disabled');
    }
  }
}

export default AnchorButton;