Marked on Google Drive

marked-google-drive.user.js

// ==UserScript==
// @name         Marked on Google Drive
// @namespace    https://github.com/yous
// @version      1.1.0
// @description  Render markdown preview on Google Drive
// @author       yous
// @homepageURL  https://gist.github.com/yous/0b48b98352215ab22eb8591b78f39361
// @updateURL    https://gist.github.com/yous/0b48b98352215ab22eb8591b78f39361/raw/marked-google-drive.user.js
// @downloadURL  https://gist.github.com/yous/0b48b98352215ab22eb8591b78f39361/raw/marked-google-drive.user.js
// @license      MIT
// @match        https://drive.google.com/file/*
// ==/UserScript==

(function() {
    'use strict';

    function loadLink(url) {
        var link = document.createElement('link');
        link.rel = 'stylesheet';
        link.href = url;
        document.body.appendChild(link);
    }

    function loadScript(url, callback) {
        var script = document.createElement('script');
        script.src = url;
        if (callback) {
            script.onload = callback;
        }
        document.body.appendChild(script);
    }

    function main() {
        var pre = document.querySelector('div[role="document"]>pre');
        if (!pre) {
            setTimeout(main, 500);
            return;
        }

        var highlightLoaded = false;
        loadLink('https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.7.0/build/styles/default.min.css');
        loadScript('https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.7.0/build/highlight.min.js', function() {
            highlightLoaded = true;
        });

        function markedOnLoad() {
            if (!highlightLoaded) {
                setTimeout(markedOnLoad, 500);
                return;
            }
            marked.setOptions({
                highlight: function(code, lang) {
                    var language = hljs.getLanguage(lang) ? lang : 'plaintext';
                    return hljs.highlight(code, { language: language }).value;
                }
            });
            pre.innerHTML = marked.parse(pre.textContent);
        }
        loadScript('https://cdn.jsdelivr.net/npm/marked@4.3.0/marked.min.js', markedOnLoad);
    }

    main();
})();