jQuery/Javascript - How to wait for manipulated DOM to update before proceeding with function

Question

What I\'m trying to do is to update a simple div to say \"Processing...\" before executing a CPU-intensive script (it takes 3-12 seconds to run, no AJAX) then update the div

Answer 1

As of 2019 one uses double requesAnimationFrame to skip a frame instead of creating a race condition using setTimeout.

....
function doRun() {
    document.getElementById('msg').innerHTML = 'Processing JS...';
    requestAnimationFrame(() =>
    requestAnimationFrame(function(){
         start = new Date();
         end = addSecs(start,5);
         do {start = new Date();} while (end-start > 0);
         document.getElementById('msg').innerHTML = 'Finished Processing';   
    }))
}
...