How to force repaint in JS?

Question

What I am trying to achieve:

1. user clicks on an element
2. the screen shows the \"calculation in progress\" screen
3. the system performs time-consu

Answer 1

You need to either wait a millisecond or do the calculations with a Worker.

The first example is probably the easiest, instead of calling calc directly, create a new function

function caller() {
     // insert "calculation in progress" in the body
    setTimeout(calc, 1);
}

Then call caller.