Download PDF file from smartedu

smartedu-download-pdf.user.js

// ==UserScript==
// @name         Download PDF from smartedu
// @namespace    https://helloint.com
// @version      0.2
// @description  Download PDF file from basic.smartedu.cn by press keyboard 'ddd'
// @author       Wayne Mao
// @match        https://basic.smartedu.cn/*
// @icon         https://www.google.com/s2/favicons?sz=64&domain=web.app
// @grant        none
// ==/UserScript==

const PASSWORD = 'ddd';
const TIMEOUT = 5000;

let userInput = '';
let iid = 0;

const startTimer = () => {
    iid = setTimeout(() => {
        userInput = '';
    }, TIMEOUT);
};

const clearTimer = () => {
    if (iid) {
        clearTimeout(iid);
    }
};

const resetTimer = () => {
    clearTimer();
    startTimer();
}

function downloadPDF(url, fileName) {
    console.log(`PDF url: ${url}, fileName: ${fileName}`);
    fetch(url)
        .then(response => response.blob())
        .then(blob => {
            const url = window.URL.createObjectURL(blob);
            const a = document.createElement('a');
            a.style.display = 'none';
            a.href = url;
            a.download = fileName;
            document.body.appendChild(a);
            a.click();
            window.URL.revokeObjectURL(url);
        })
        .catch(() => alert('An error occurred while downloading the PDF.'));
}

function parsePdfInfo() {
    const pdfTitle = document.querySelectorAll('h3')[0].innerText;
    const urlParams = new URLSearchParams(location.search);
    const pdfId = urlParams.get('contentId'); // c4857bdb-4166-4552-b65e-41b545d8f7b8
    const pdfUrl = `https://r3-ndr.ykt.cbern.com.cn/edu_product/esp/assets/${pdfId}.pkg/pdf.pdf`;

    return {
        pdfTitle, pdfUrl
    };
}

function doc_keyUp(e) {
    resetTimer();
    switch (e.keyCode) {
        case 68:
            //d
            userInput += 'd';
            break;
        default:
            userInput = '';
            break;
    }

    if (userInput === 'ddd') {
        const {pdfUrl, pdfTitle} = parsePdfInfo();
        downloadPDF(pdfUrl, pdfTitle);
    }
}
document.addEventListener('keyup', doc_keyUp, false);

your request become quite customized...

I understand, and I apologize for the inconvenience. For your help, thank you very much, the code was perfect with what I was looking for.