JSFiddle - React, Tailwind, and code Playground

HTML

<button type="button" id="button">Click Me!</button>

JavaScript

function myFunction(){
    flag = 0 
    console.info("initial", flag);
    setTimeout(function(){
        flag = 10;
    }, 200);
  
    confirm("conf");
   
    alert("should be 0: "+flag);
}

document.getElementById('button').onclick=myFunction;