@material/snackbar
Version:
The Material Components for the web snackbar component
86 lines • 4.53 kB
JavaScript
/**
* @license
* Copyright 2018 Google Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
import { numbers, strings } from './constants';
var ARIA_LIVE_DELAY_MS = numbers.ARIA_LIVE_DELAY_MS;
var ARIA_LIVE_LABEL_TEXT_ATTR = strings.ARIA_LIVE_LABEL_TEXT_ATTR;
function announce(ariaEl, labelEl) {
if (labelEl === void 0) { labelEl = ariaEl; }
var priority = ariaEl.getAttribute('aria-live');
// Trim text to ignore ` ` (see below).
// textContent is only null if the node is a document, DOCTYPE, or notation.
var labelText = labelEl.textContent.trim();
if (!labelText || !priority) {
return;
}
// Temporarily disable `aria-live` to prevent JAWS+Firefox from announcing the message twice.
ariaEl.setAttribute('aria-live', 'off');
// Temporarily clear `textContent` to force a DOM mutation event that will be detected by screen readers.
// `aria-live` elements are only announced when the element's `textContent` *changes*, so snackbars
// sent to the browser in the initial HTML response won't be read unless we clear the element's `textContent` first.
// Similarly, displaying the same snackbar message twice in a row doesn't trigger a DOM mutation event,
// so screen readers won't announce the second message unless we first clear `textContent`.
//
// We have to clear the label text two different ways to make it work in all browsers and screen readers:
//
// 1. `textContent = ''` is required for IE11 + JAWS
// 2. `innerHTML = ' '` is required for Chrome + JAWS and NVDA
//
// All other browser/screen reader combinations support both methods.
//
// The wrapper `<span>` visually hides the space character so that it doesn't cause jank when added/removed.
// N.B.: Setting `position: absolute`, `opacity: 0`, or `height: 0` prevents Chrome from detecting the DOM change.
//
// This technique has been tested in:
//
// * JAWS 2019:
// - Chrome 70
// - Firefox 60 (ESR)
// - IE 11
// * NVDA 2018:
// - Chrome 70
// - Firefox 60 (ESR)
// - IE 11
// * ChromeVox 53
labelEl.textContent = '';
// For the second case, assigning a string directly to innerHTML results in a
// Trusted Types violation. Work around that by using document.createElement.
var span = document.createElement('span');
span.setAttribute('style', 'display: inline-block; width: 0; height: 1px;');
span.textContent = '\u00a0'; // Equivalent to
labelEl.appendChild(span);
// Prevent visual jank by temporarily displaying the label text in the ::before pseudo-element.
// CSS generated content is normally announced by screen readers
// (except in IE 11; see https://tink.uk/accessibility-support-for-css-generated-content/);
// however, `aria-live` is turned off, so this DOM update will be ignored by screen readers.
labelEl.setAttribute(ARIA_LIVE_LABEL_TEXT_ATTR, labelText);
setTimeout(function () {
// Allow screen readers to announce changes to the DOM again.
ariaEl.setAttribute('aria-live', priority);
// Remove the message from the ::before pseudo-element.
labelEl.removeAttribute(ARIA_LIVE_LABEL_TEXT_ATTR);
// Restore the original label text, which will be announced by screen readers.
labelEl.textContent = labelText;
}, ARIA_LIVE_DELAY_MS);
}
export { announce };
//# sourceMappingURL=util.js.map