JSFiddle - React, Tailwind, and code Playground

HTML

<div id="output"></div>

JavaScript

var counter;

function longRun(start) {
    counter = 0;
    
    for (var i = start; i < 3000; i++) {

        counter++;
        console.log(i);
        if (counter > 99) {
            setTimeout(function() {
                longRun(i+1)
            }, 0);
                console.log('counter at: ' + i + ' start fake "thread"');
            return;
        }
    }
    alert('Done!');
}
longRun(0);