75 lines
3.1 KiB
JavaScript
75 lines
3.1 KiB
JavaScript
/**
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* @license
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* Copyright (c) 2017 The Polymer Project Authors. All rights reserved.
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* This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
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* The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
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* The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
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* Code distributed by Google as part of the polymer project is also
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* subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
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*/
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(function() {
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'use strict';
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// global for (1) existence means `WebComponentsReady` will file,
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// (2) WebComponents.ready == true means event has fired.
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window.WebComponents = window.WebComponents || {};
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var name = 'webcomponents-loader.js';
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// Feature detect which polyfill needs to be imported.
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var polyfills = [];
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if (!('import' in document.createElement('link'))) {
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polyfills.push('hi');
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}
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if (!('attachShadow' in Element.prototype && 'getRootNode' in Element.prototype) ||
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(window.ShadyDOM && window.ShadyDOM.force)) {
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polyfills.push('sd');
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}
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if (!window.customElements || window.customElements.forcePolyfill) {
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polyfills.push('ce');
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}
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// NOTE: any browser that does not have template or ES6 features
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// must load the full suite (called `lite` for legacy reasons) of polyfills.
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if (!('content' in document.createElement('template')) || !window.Promise || !Array.from ||
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// Edge has broken fragment cloning which means you cannot clone template.content
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!(document.createDocumentFragment().cloneNode() instanceof DocumentFragment)) {
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polyfills = ['lite'];
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}
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if (polyfills.length) {
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var script = document.querySelector('script[src*="' + name +'"]');
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var newScript = document.createElement('script');
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// Load it from the right place.
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var replacement = 'webcomponents-' + polyfills.join('-') + '.js';
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var url = script.src.replace(name, replacement);
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newScript.src = url;
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// NOTE: this is required to ensure the polyfills are loaded before
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// *native* html imports load on older Chrome versions. This *is* CSP
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// compliant since CSP rules must have allowed this script to run.
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// In all other cases, this can be async.
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if (document.readyState === 'loading' && ('import' in document.createElement('link'))) {
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document.write(newScript.outerHTML);
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} else {
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document.head.appendChild(newScript);
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}
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} else {
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// Ensure `WebComponentsReady` is fired also when there are no polyfills loaded.
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// however, we have to wait for the document to be in 'interactive' state,
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// otherwise a rAF may fire before scripts in <body>
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var fire = function() {
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requestAnimationFrame(function() {
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window.WebComponents.ready = true;
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document.dispatchEvent(new CustomEvent('WebComponentsReady', {bubbles: true}));
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});
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};
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if (document.readyState !== 'loading') {
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fire();
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} else {
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document.addEventListener('readystatechange', function wait() {
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fire();
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document.removeEventListener('readystatechange', wait);
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});
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}
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}
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})();
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