Does inline javascript block the UI thread?

Question

I read this nice article on how external scripts block the UI thread but it wasn\'t clear to me whether the blocking is actually due to the presence of the

Answer 1

alert() or any other prompting actions will block the thread until the user responds to the prompt. No matter where they are...

Update ( regarding the comment ) :

A browser window parses the HTML and runs the JS with a single thread.. so anything in the javascript code that will take time to complete will block the thread.. no matter what it is.. It can be an alert or an AJAX Request or anything else..