How can I close window when the download is finished?

Question

I am using a recent version of ANGULAR and all I want to achieve is to close the window when the download is finished.

It is supposed to work like this: when the user clicks on a link it opens this window that makes the download start and then it closes when download is finished, so that the close of the window doesn't stop the download.

I got this all sorted out for the main browsers except IE11, but I really need this to work on IE11.

This is what I have:

startDownload(filename: string, filecontent: string) {

    let blob = DownloadUtils.b64toBlob(filecontent, "application/pdf");

    let blobUrl = window.URL.createObjectURL(blob);

    var downloadID = (new Date()).getTime();

    var a = document.createElement('a');
    a.setAttribute('href', blobUrl + "#downloadID=" + downloadID);
    a.setAttribute('download', filename);

    this.cookiePattern = new RegExp(("downloadID=" + downloadID), "i");
    this.checkCookies();

    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);

    window.URL.revokeObjectURL(blobUrl);
}

checkCookies() {

    if (document.cookie.search(this.cookiePattern) >= 0) {
        open('', '_self').close(); // download complete -> close window
        return;
    }

    setTimeout(this.checkCookies, 500);
}

I was inspired by: https://laracasts.com/discuss/channels/javascript/using-javascript-to-check-if-a-file-has-been-downloaded

The problem with IE11 is that it doesn´t allow the download of blob URLs, I guess.

IE11 forces the use of:

window.navigator.msSaveBlob(blob, filename);

But with this I cant use the queryString "downloadID" to detect the end of download.

I also tried FileSaver.js but didn´t work.

I also tried to set:

a.setAttribute('href', 'data:application/pdf;base64,' + filecontent + "#downloadID=" + downloadID);

Which works, except on IE11 again. I get this error:

"The data area passed to a system call is too small."

NOTE: The problem isn't closing the page, but knowing when to close.

I could use a timeout for IE11, but I rather not.

Can you please help?