JSFiddle - React, Tailwind, and code Playground

HTML

<div>Ordered array run took <span id='o'></span> msec.</div>
<div>Not ordered array run took <span id='no'></span> msec.</div>

CSS

body { background-color: #247; }
div { color: #fff; }

JavaScript

const size = 100000;
const timesToRepeat = 1000;
const measure = function(id, func) {
	const t0 = performance.now();
  for (j = 0; j < timesToRepeat; j++) {
    func();
  }
  const t1 = performance.now();
  document.getElementById(id).innerText = Math.floor(t1 - t0);
};

const iterate = function(array) {
  var sum = 0;
  for (i = 0; i < size; i++) {
    if (array[i] < (size / 2)) {
      sum += array[i];
    }
  }
  return sum;
};

const notOrdered = Array.from({length: size}, () => Math.floor(Math.random() * size));
const ordered = Array.from({length: size}, (v, k) => k);

measure("o", function() { iterate(ordered); });
measure("no", function() { iterate(notOrdered); });