https://www.bndes.gov.br/pelev2/webcomponentsjs/webcomponents-loader.js

1/**
2 * @license
3 * Copyright (c) 2018 The Polymer Project Authors. All rights reserved.
4 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
5 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
6 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
7 * Code distributed by Google as part of the polymer project is also
8 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
9 */
10
11(function () {
12  'use strict';
13
14  /**
15   * Basic flow of the loader process
16   *
17   * There are 4 flows the loader can take when booting up
18   *
19   * - Synchronous script, no polyfills needed
20   *   - wait for `DOMContentLoaded`
21   *   - fire WCR event, as there could not be any callbacks passed to `waitFor`
22   *
23   * - Synchronous script, polyfills needed
24   *   - document.write the polyfill bundle
25   *   - wait on the `load` event of the bundle to batch Custom Element upgrades
26   *   - wait for `DOMContentLoaded`
27   *   - run callbacks passed to `waitFor`
28   *   - fire WCR event
29   *
30   * - Asynchronous script, no polyfills needed
31   *   - wait for `DOMContentLoaded`
32   *   - run callbacks passed to `waitFor`
33   *   - fire WCR event
34   *
35   * - Asynchronous script, polyfills needed
36   *   - Append the polyfill bundle script
37   *   - wait for `load` event of the bundle
38   *   - batch Custom Element Upgrades
39   *   - run callbacks pass to `waitFor`
40   *   - fire WCR event
41   */
42
43  var polyfillsLoaded = false;
44  var whenLoadedFns = [];
45  var allowUpgrades = false;
46  var flushFn;
47
48  function fireEvent() {
49    window.WebComponents.ready = true;
50    document.dispatchEvent(
51      new CustomEvent('WebComponentsReady', {bubbles: true})
52    );
53  }
54
55  function batchCustomElements() {
56    if (window.customElements && customElements.polyfillWrapFlushCallback) {
57      customElements.polyfillWrapFlushCallback(function (flushCallback) {
58        flushFn = flushCallback;
59        if (allowUpgrades) {
60          flushFn();
61        }
62      });
63    }
64  }
65
66  function asyncReady() {
67    batchCustomElements();
68    ready();
69  }
70
71  function ready() {
72    // bootstrap <template> elements before custom elements
73    if (window.HTMLTemplateElement && HTMLTemplateElement.bootstrap) {
74      HTMLTemplateElement.bootstrap(window.document);
75    }
76    polyfillsLoaded = true;
77    runWhenLoadedFns().then(fireEvent);
78  }
79
80  function runWhenLoadedFns() {
81    allowUpgrades = false;
82    var fnsMap = whenLoadedFns.map(function (fn) {
83      return fn instanceof Function ? fn() : fn;
84    });
85    whenLoadedFns = [];
86    return Promise.all(fnsMap)
87      .then(function () {
88        allowUpgrades = true;
89        flushFn && flushFn();
90      })
91      .catch(function (err) {
92        console.error(err);
93      });
94  }
95
96  window.WebComponents = window.WebComponents || {};
97  window.WebComponents.ready = window.WebComponents.ready || false;
98  window.WebComponents.waitFor =
99    window.WebComponents.waitFor ||
100    function (waitFn) {
101      if (!waitFn) {
102        return;
103      }
104      whenLoadedFns.push(waitFn);
105      if (polyfillsLoaded) {
106        runWhenLoadedFns();
107      }
108    };
109  window.WebComponents._batchCustomElements = batchCustomElements;
110
111  var name = 'webcomponents-loader.js';
112  // Feature detect which polyfill needs to be imported.
113  var polyfills = [];
114  if (
115    !(
116      'attachShadow' in Element.prototype && 'getRootNode' in Element.prototype
117    ) ||
118    (window.ShadyDOM && window.ShadyDOM.force)
119  ) {
120    polyfills.push('sd');
121  }
122  if (!window.customElements || window.customElements.forcePolyfill) {
123    polyfills.push('ce');
124  }
125
126  var needsTemplate = (function () {
127    // no real <template> because no `content` property (IE and older browsers)
128    var t = document.createElement('template');
129    if (!('content' in t)) {
130      return true;
131    }
132    // broken doc fragment (older Edge)
133    if (!(t.content.cloneNode() instanceof DocumentFragment)) {
134      return true;
135    }
136    // broken <template> cloning (Edge up to at least version 17)
137    var t2 = document.createElement('template');
138    t2.content.appendChild(document.createElement('div'));
139    t.content.appendChild(t2);
140    var clone = t.cloneNode(true);
141    return (
142      clone.content.childNodes.length === 0 ||
143      clone.content.firstChild.content.childNodes.length === 0
144    );
145  })();
146
147  // NOTE: any browser that does not have template or ES6 features
148  // must load the full suite of polyfills.
149  if (
150    !window.Promise ||
151    !Array.from ||
152    !window.URL ||
153    !window.Symbol ||
154    needsTemplate
155  ) {
156    polyfills = ['sd-ce-pf'];
157  }
158
159  if (polyfills.length) {
160    var url;
161    var polyfillFile = 'bundles/webcomponents-' + polyfills.join('-') + '.js';
162
163    // Load it from the right place.
164    if (window.WebComponents.root) {
165      url = window.WebComponents.root + polyfillFile;
166    } else {
167      var script = document.querySelector('script[src*="' + name + '"]');
168      // Load it from the right place.
169      url = script.src.replace(name, polyfillFile);
170    }
171
172    var newScript = document.createElement('script');
173    newScript.src = url;
174    // if readyState is 'loading', this script is synchronous
175    if (document.readyState === 'loading') {
176      // make sure custom elements are batched whenever parser gets to the injected script
177      newScript.setAttribute(
178        'onload',
179        'window.WebComponents._batchCustomElements()'
180      );
181      document.write(newScript.outerHTML);
182      document.addEventListener('DOMContentLoaded', ready);
183    } else {
184      newScript.addEventListener('load', function () {
185        asyncReady();
186      });
187      newScript.addEventListener('error', function () {
188        throw new Error('Could not load polyfill bundle' + url);
189      });
190      document.head.appendChild(newScript);
191    }
192  } else {
193    // if readyState is 'complete', script is loaded imperatively on a spec-compliant browser, so just fire WCR
194    if (document.readyState === 'complete') {
195      polyfillsLoaded = true;
196      fireEvent();
197    } else {
198      // this script may come between DCL and load, so listen for both, and cancel load listener if DCL fires
199      window.addEventListener('load', ready);
200      window.addEventListener('DOMContentLoaded', function () {
201        window.removeEventListener('load', ready);
202        ready();
203      });
204    }
205  }
206})();