Iframe.readyState does not work in chrome

Question

I create an Iframe on the fly and set as the url a page that downloads a binary file (xls, doc...). While files are downloading I show an animation. When do

Answer 1

Sarkiroka's solution worked for me. I have added an instance id to the cookie name to provide a thread safe solution:

const instanceId = "some uuid retrieved from client";

response.cookie(`fileDownloaded-${instanceId}`,'true', { path: '/', secure: true, maxAge: 90000});
response.header('attachment','your-file-name.any');
//...write bytes to response...

client

var checker = setInterval(()=>{
    if(document.cookie.indexOf(`fileDownloaded-${instanceId}`)>-1){
        alert('done');
        clearInterval(checker);
    }
},100);