我正在尝试构建一个简单的节点快速应用程序，以使用ytdl-core从youtube下载视频，但由于某些原因，我的代码无法正常工作。 我几乎尝试了所有操作，该应用程序收到了请求，但不执行任何操作，页面似乎已刷新，但没有下载开始。

script.js

var confirmText = "Downloading videos from YouTube is against the YouTube Policy.\n"
                    + "The only videos that your allowed to download is your own.";


function downloadVideo() {
    if (confirm(confirmText)){
        var URLinput = document.getElementById("URL-input").value;
        var req = new XMLHttpRequest();
        req.open('get','/download?url=' + URLinput,false);
        req.send();
    }
}

index.js

const express = require('express');
const path = require('path');
const cors = require('cors');
const ytdl = require('ytdl-core');
const app = express();

app.use(cors());
app.use(express.static("public"));

app.listen(4000,() => {
    console.log('Server Works !!! At port 4000');
});

app.get('/',(req,res) => {
    res.sendFile(path.join(__dirname,'public','index.html'));
});

app.get('/download',res) => {
    var url_input = req.query.url;
    console.log(url_input);
    res.header('Content-Disposition','attachment; filename="video.mp4"');
    ytdl(url_input,{format: 'mp4'}).pipe(res);
});

app.get('*','404.html'));
});