JSFiddle - React, Tailwind, and code Playground

HTML

<div id="output"></div>
<button onclick="updateSync()">Run Sync</button>
<button onclick="updateAsync()">Run Async</button>

JavaScript

function updateSync() {
    for (var i = 0; i < 1000; i++) {
        document.getElementById('output').innerHTML = i;
    }
}

function updateAsync() {
    var i = 0;

    function updateLater() {
        document.getElementById('output').innerHTML = (i++);
        if (i < 1000) {
            setTimeout(updateLater, 0);
        }
    }

    updateLater();
}