How to force UI draw in ElectronJS prior to intense computation task?

I am building an Electron program to identify molecular ions from precise mass determinations. The calculation can take several seconds or even a few minutes. To let the user know that it is processing, I would like to change the text on the button that starts the calculation to “Processing…” before the intense calculation begins. But Everything I try results in the change being displayed after the calculation completes!

In principle I thought this would work, as a similar code works for reading the atomic mass database before parsing it.

function fnFindSCM(){

  async function showProcessing() {
    document.getElementById("btnFindSCM").innerHTML = "Processing...";   
  }

  async function awaitShowProcessing(){
    await showProcessing();

  }

  awaitShowProcessing();

  reallyFindSCM();

}

The function fnFindSCM() is the button’s click event listener, while reallyFindSCM() is the function that does the heavy calculations.

I am hoping that a solution to this problem will also solve my next problem — displaying “hits” as they are found rather than all at once when the search is complete.