counter

Creates a counter with the specified range, step and duration for the specified selector.

• Check if step has the proper sign and change it accordingly.
• Use setInterval() in combination with Math.abs() and Math.floor() to calculate the time between each new text draw.
• Use Document.querySelector(), Element.innerHTML to update the value of the selected element.
• Omit the fourth argument, step, to use a default step of 1.
• Omit the fifth argument, duration, to use a default duration of 2000ms.

const counter = (selector, start, end, step = 1, duration = 2000) => {
  let current = start,
    _step = (end - start) * step < 0 ? -step : step,
    timer = setInterval(() => {
      current += _step;
      document.querySelector(selector).innerHTML = current;
      if (current >= end) document.querySelector(selector).innerHTML = end;
      if (current >= end) clearInterval(timer);
    }, Math.abs(Math.floor(duration / (end - start))));
  return timer;
};

counter('#my-id', 1, 1000, 5, 2000);
// Creates a 2-second timer for the element with id="my-id"