JSFiddle - React, Tailwind, and code Playground

HTML

<div>current delay in ms: <span id="delay"></span></div>
<div>highest registered delay in ms: <span id="hdelay"></span></div>


<button>Start random computation</button>
<div id="log"></div>

JavaScript

var expected = new Date().getTime() + 200;
var highestDelay = 0;
var delayDisplay = document.getElementById("delay");
var highestDelayDisplay = document.getElementById("hdelay");
function check(){
    var delay = new Date().getTime() - expected;
    delay = delay >= 0 ? delay : 0;
    if(delay > highestDelay) highestDelay = delay;
    delayDisplay.textContent = delay;
    highestDelayDisplay.textContent = highestDelay;
    expected = new Date().getTime() + 200;
}
setInterval(check, 200);






var log = document.getElementById("log");
var button = document.getElementsByTagName("button")[0];
button.addEventListener("click", function(){
    var sieve = [], i, j, max = 100000;
    for (i = 2; i <= max; ++i) {
        if (!sieve[i]) {
            // i has not been marked -- it is prime
            log.textContent += " - " + i;
            for (j = i << 1; j <= max; j += i) {
                sieve[j] = true;
            }
        }
    }
});