JS 指定选择器创建具有指定范围，步长和持续时间的计数器

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;
};

// 事例
counter('#my-id', 1, 1000, 5, 2000); 
// 让 `id=“my-id”`的元素创建一个2秒计时器