js prompt browser download dialog
function downloadFile(file) {
// Create a link and set the URL using `createObjectURL`
const link = document.createElement("a");
link.style.display = "none";
link.href = URL.createObjectURL(file);
link.download = file.name;
// It needs to be added to the DOM so it can be clicked
document.body.appendChild(link);
link.click();
// To make this work on Firefox we need to wait
// a little while before removing it.
setTimeout(() => {
URL.revokeObjectURL(link.href);
link.parentNode.removeChild(link);
}, 0);
}