Hey Srikanth,

You are asking a very difficult question as you can't really access the browser information like that.

A possible workaround is using a cookie, but unfortunately that's a no go for you....

What's left is storing the entire blob in memory.
Basically, when the user clicks a button, you run a bit of javascript which downloads the file (using fetch()) after it's finished you notify the user by making changes to the DOM or an alert or something.

Example:

async function downloadFile(url) {
    var response = await fetch(url);
    var blob = await response.blob();

    return blob;
}

.....
downloadFile('https://site.com/myfile.exe').then(blob => {
    // trigger a message here that the file is finished downloading, or whatever you want to do
    // with the code below you can directly download the file to the users device
    var url = window.URL.createObjectURL(blob);
    var a = document.createElement('a');
    a.href = url;
    a.download = 'myfile.exe';
    document.body.appendChild(a); // fix for firefox
    a.click();
    a.remove();
});
.....

then() triggers after an async function has completed.
The big problem with this solution, is that if you download a file of several GB's, it will be put into the users memory. So for very big files this won't work.