get_data.js

var r = [];

for (var i = 0; i < a.length; i++) {
    var httpRequest = new XMLHttpRequest();
    r.push(httpRequest);
    var url = a[i];
    
    httpRequest.onreadystatechange = () => {
        var t = document.createElement("t");
        var url_title = document.createElement("p");
        url_title.innerText = url;

        if (httpRequest.readyState == 4)
        {
            t.innerHTML = httpRequest.response;
            t = t.querySelector("table");

            document.body.appendChild(url_title);
            document.body.appendChild(t);
        }
        else
        {
            console.log(url);
        }
    };

    httpRequest.open("GET", url, true);
    httpRequest.send();
    await new Promise(r => setTimeout(r, 500));
}

for (var i = 0; i < r.length; i++) {
    var httpRequest = r[i];
    
    if (httpRequest.readyState != 4)
    {
        console.log(url);
    }
}