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A Custom Element radio group which demonstrates roving tabindex
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| <!-- | |
| Copyright 2016 Google Inc. All rights reserved. | |
| Licensed 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 CONDITIONS OF ANY KIND, either express or implied. | |
| See the License for the specific language governing permissions and | |
| limitations under the License. | |
| --> | |
| <style> | |
| .demo { | |
| margin-left: 80px; | |
| } | |
| radio-button { | |
| position: relative; | |
| display: block; | |
| font-size: 18px; | |
| } | |
| radio-button:focus { | |
| outline: none; | |
| } | |
| radio-button::before { | |
| content: ''; | |
| display: block; | |
| width: 10px; | |
| height: 10px; | |
| border: 1px solid black; | |
| position: absolute; | |
| left: -18px; | |
| top: 7px; | |
| border-radius: 50%; | |
| } | |
| radio-button:focus::before { | |
| box-shadow: 0 0 3px 3px #83BEFF; | |
| } | |
| radio-button[aria-checked="true"]::before { | |
| content: ''; | |
| display: block; | |
| width: 10px; | |
| height: 10px; | |
| background: red; | |
| position: absolute; | |
| left: -18px; | |
| top: 7px; | |
| border-radius: 50%; | |
| } | |
| </style> | |
| <div class="demo"> | |
| <radio-group> | |
| <radio-button>Water</radio-button> | |
| <radio-button>Coffee</radio-button> | |
| <radio-button>Tea</radio-button> | |
| <radio-button>Cola</radio-button> | |
| <radio-button>Ginger Ale</radio-button> | |
| </radio-group> | |
| </div> | |
| <script src="https://cdn.rawgit.com/webcomponents/custom-elements/master/custom-elements.min.js"></script> | |
| <script> | |
| class RadioButton extends HTMLElement { | |
| constructor() { | |
| super(); | |
| } | |
| connectedCallback() { | |
| this.setAttribute('role', 'radio'); | |
| this.setAttribute('tabindex', -1); | |
| this.setAttribute('aria-checked', false); | |
| } | |
| } | |
| window.customElements.define('radio-button', RadioButton); | |
| // Define values for keycodes | |
| const VK_LEFT = 37; | |
| const VK_UP = 38; | |
| const VK_RIGHT = 39; | |
| const VK_DOWN = 40; | |
| class RadioGroup extends HTMLElement { | |
| constructor() { | |
| super(); | |
| } | |
| connectedCallback() { | |
| this.setAttribute('role', 'radiogroup'); | |
| this.radios = Array.from(this.querySelectorAll('radio-button')); | |
| // Setup initial state | |
| if (this.hasAttribute('selected')) { | |
| let selected = this.getAttribute('selected'); | |
| this._selected = selected; | |
| this.radios[selected].setAttribute('tabindex', 0); | |
| this.radios[selected].setAttribute('aria-checked', true); | |
| } else { | |
| this._selected = 0; | |
| this.radios[0].setAttribute('tabindex', 0); | |
| } | |
| this.addEventListener('keydown', this.handleKeyDown.bind(this)); | |
| this.addEventListener('click', this.handleClick.bind(this)); | |
| } | |
| handleKeyDown(e) { | |
| switch(e.keyCode) { | |
| case VK_UP: | |
| case VK_LEFT: { | |
| e.preventDefault(); | |
| if (this.selected === 0) { | |
| this.selected = this.radios.length - 1; | |
| } else { | |
| this.selected--; | |
| } | |
| break; | |
| } | |
| case VK_DOWN: | |
| case VK_RIGHT: { | |
| e.preventDefault(); | |
| if (this.selected === this.radios.length - 1) { | |
| this.selected = 0; | |
| } else { | |
| this.selected++; | |
| } | |
| break; | |
| } | |
| } | |
| } | |
| handleClick(e) { | |
| const idx = this.radios.indexOf(e.target); | |
| if (idx === -1) { | |
| return; | |
| } | |
| this.selected = idx; | |
| } | |
| set selected(idx) { | |
| if (isFinite(this.selected)) { | |
| // Set the old button to tabindex -1 | |
| let previousSelected = this.radios[this.selected]; | |
| previousSelected.tabIndex = -1; | |
| previousSelected.removeAttribute('aria-checked', false); | |
| } | |
| // Set the new button to tabindex 0 and focus it | |
| let newSelected = this.radios[idx]; | |
| newSelected.tabIndex = 0; | |
| newSelected.focus(); | |
| newSelected.setAttribute('aria-checked', true); | |
| this.setAttribute('selected', idx); | |
| this._selected = idx; | |
| } | |
| get selected() { | |
| return this._selected; | |
| } | |
| } | |
| window.customElements.define('radio-group', RadioGroup); | |
| </script> |
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