Tapermonkey script that adds the download button to lectures on NYJCPortal/NYPortal

Download.js

// ==UserScript==
// @name         NYJC download
// @namespace    https://tampermonkey.net/
// @version      2025-03-02
// @description  Adds the download button to lectures on the NYJCportal. https://gist.github.com/lomnom/a0c51d25a65198eba13333d6395e9bb1
// @author       lomnom on github
// @match        portal.nyjc.edu.sg/*
// @icon         data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==
// @grant        none
// ==/UserScript==

'use strict';

// Template to put id into to make download button.
// In form before + id + after = button HTML
// Copied from source of the other buttons
const buttonTemplate = {
    before: '<a class="btn btn-xs btn-success" href="javascript:void(0)" onclick="$Page.variables().download(\'',
    after: '\')"><i class="fa fa-download"></i> Download</a> '
}

/*
The .download() call makes the same API request as the .video_view call, which supposedly
registers who has watched the lecture.
*/

// Padding
const padding = "<a style='visibility: hidden'>I</a>";

function main(){
    const buttons = document.querySelectorAll("a.btn");
    for (var index = 0; index<buttons.length; index++){
        var button = buttons[index];
        // Ensure button is a "Watch online button."
        if (!button.innerHTML.endsWith("Watch Online")){
            continue;
        }

        // Ensure button has not already been processed
        if (button.classList.contains("download-added")){
            continue;
        }
        // Flag the button as processed
        button.classList.add("download-added");

        var id = button.onclick.toString().split("'")[1]; // The id of the video

        var addedButton = padding + buttonTemplate.before + id + buttonTemplate.after;
        // console.log(addedButton);
        console.log("Download button added for " + id)
        button.insertAdjacentHTML('afterend', addedButton);
    }
}

const pollTime = 750; // How often a check is done for new buttons
setInterval(main, pollTime);