A question on URL.createObjectURL

Hi all,
I have a question on the browser API `URL.createObjectURL`
https://github.com/eligrey/FileSaver.js/blob/master/src/FileSaver.js#L106
```
a.href = URL.createObjectURL(blob)
setTimeout(function () { URL.revokeObjectURL(a.href) }, 4E4) // 40s
setTimeout(function () { click(a) }, 0)
```
What the purpose here by putting the `click` into the `setTimeout` function?

I found there's some problem when call `click` in sync way
[https://jsfiddle.net/1c8fnvwk/2/](https://jsfiddle.net/1c8fnvwk/2/)
But I didn't find any post describing the root cause.