forked from webcomponents/webcomponentsjs
/
webcomponents-loader.js
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/
webcomponents-loader.js
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/**
* @license
* Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
* This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
* The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
* The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
* Code distributed by Google as part of the polymer project is also
* subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
*/
(function() {
'use strict';
var name = 'webcomponents-loader.js';
// Feature detect which polyfill needs to be imported.
var polyfills = [];
if (!('import' in document.createElement('link'))) {
polyfills.push('hi');
}
if (!('attachShadow' in Element.prototype && 'getRootNode' in Element.prototype) ||
(window.ShadyDOM && window.ShadyDOM.force)) {
polyfills.push('sd');
}
if (!window.customElements || window.customElements.forcePolyfill) {
polyfills.push('ce');
}
if (!('content' in document.createElement('template')) || !window.Promise ||
// Edge has broken fragment cloning which means you cannot clone template.content
!(document.createDocumentFragment().cloneNode() instanceof DocumentFragment)) {
polyfills.push('pf');
}
if (polyfills.length === 4) { // hi-ce-sd-pf is actually called lite.
polyfills = ['lite'];
}
// NOTE: we stub HTMLImports to enable WCT to wait for "WebComponentsReady" event.
window['HTMLImports'] = {};
if (polyfills.length) {
var script = document.querySelector('script[src*="' + name +'"]');
var newScript = document.createElement('script');
// Load it from the right place.
var replacement = 'webcomponents-' + polyfills.join('-') + '.js';
var url = script.src.replace(name, replacement);
newScript.src = url;
document.head.appendChild(newScript);
} else {
// Ensure `WebComponentsReady` is fired also when there are no polyfills loaded.
requestAnimationFrame(function() {
// Reset the HTMLImports stub.
window['HTMLImports'] = null;
window.dispatchEvent(new CustomEvent('WebComponentsReady'));
});
}
})();