talos

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/*
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 * Copyright 2018 Google LLC
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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    https://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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(function ($) {
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    'use strict';
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    // Headers' anchor link that shows on hover
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    $(function () {
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        // append anchor links to headings in markdown.
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        var article = document.getElementsByTagName('main')[0];
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        if (!article) {
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            return;
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        }
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        var headings = article.querySelectorAll('h1, h2, h3, h4, h5, h6');
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        headings.forEach(function (heading) {
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            if (heading.id) {
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                var a = document.createElement('a');
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                // set visibility: hidden, not display: none to avoid layout change
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                a.style.visibility = 'hidden';
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                // [a11y] hide this from screen readers, etc..
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                a.setAttribute('aria-hidden', 'true');
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                // material insert_link icon in svg format
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                a.innerHTML = ' <svg xmlns="http://www.w3.org/2000/svg" fill="currentColor" width="24" height="24" viewBox="0 0 24 24"><path d="M0 0h24v24H0z" fill="none"/><path d="M3.9 12c0-1.71 1.39-3.1 3.1-3.1h4V7H7c-2.76 0-5 2.24-5 5s2.24 5 5 5h4v-1.9H7c-1.71 0-3.1-1.39-3.1-3.1zM8 13h8v-2H8v2zm9-6h-4v1.9h4c1.71 0 3.1 1.39 3.1 3.1s-1.39 3.1-3.1 3.1h-4V17h4c2.76 0 5-2.24 5-5s-2.24-5-5-5z"/></svg>';
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                a.href = '#' + heading.id;
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                heading.insertAdjacentElement('beforeend', a);
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                heading.addEventListener('mouseenter', function () {
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                    a.style.visibility = 'initial';
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                });
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                heading.addEventListener('mouseleave', function () {
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                    a.style.visibility = 'hidden';
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                });
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            }
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        });
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    });
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}(jQuery));
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