I am using Angular 5 and have a fairly straightforward example of a spreadsheet that I am creating. It is about 20 rows and 100 columns. It works like a charm in Chrome, but when I test it in IE11 (unfortunately, IE is my company's standard browser), it is painfully slow. It churns my CPU at about 35% for the entire time also, and my memory monitor fluxing up and down wildly.

My code to write on the client looks like this (I have seen this example many times in these issues discussions):

wb.xlsx.writeBuffer().then( data => {
const blob = new Blob( [data], { type: 'application/octet-stream'} );
saveAs( blob, "myFile.xlsx");
});

I am using the file-saver library and saveAs. But the slow part is getting into the .then() of the writeBuffer() function. In Chrome, getting into this callback is almost instantaneous while in IE it is over 35 seconds!
I have tried this on a couple of different Windows machines (7 and 10) and different hardware, with similar results.
Has anyone seen this behavior?