A userscript which adds a "View" button to STL files on prusaprinters.org

prusaprinters_stl_viewer.user.js

// ==UserScript==
// @name         PrusaPrinters STL Viewer
// @namespace    http://literalchaos.de
// @version      1.0
// @description  Add a "View STL" button to prusaprinters.org
// @author       jangxx
// @match        https://www.prusaprinters.org/prints/*
// @grant        none
// @downloadURL  https://gist.github.com/jangxx/dfb47c3dd8f1ee98cce067d5098733c3/raw/prusaprinters_stl_viewer.user.js
// ==/UserScript==

(function() {
    'use strict';

    let currentlyInjected = false;

    setInterval(function() {
        const dlNode = document.querySelector("market-downloads");

        if (dlNode == undefined) {
            currentlyInjected = false;
            return;
        }

        if (currentlyInjected) return;

        const dlItems = dlNode.querySelectorAll(".download-item");

        dlItems.forEach(elem => {
            const downloadUrl = elem.querySelector(".btn-download").href;

            const viewButton = document.createElement("a");
            viewButton.href = "https://3dviewer.net/#" + downloadUrl;
            viewButton.target = "_blank";
            viewButton.className = "btn btn-primary";
            viewButton.innerHTML = `<i class="fa fa-eye"></i><span style="display: block; font-size: .6875rem;">View</span>`;
            viewButton.style.cssText = "padding-bottom: .25rem; padding-top: 0; font-size: 1.25rem";

            const wrapper = document.createElement("div");
            wrapper.className = "download-wrapper";
            wrapper.style.marginRight = "0.2rem";

            wrapper.appendChild(viewButton);

            elem.insertBefore(wrapper, elem.querySelector(".download-wrapper"));
        });

        currentlyInjected = true;
    }, 500);
})();