<div id="progress"></div>

<script>
  let i = 0;

  function count() {

    // القيام بجزء من مهمّة ثقيلة (*)
    do {
      i++;
      progress.innerHTML = i;
    } while (i % 1e3 != 0);

    if (i < 1e6) {
      queueMicrotask(count);
    }

  }

  count();
</script>
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