JS判断dom元素是否在可视范围内

function isElementInViewport (el, offset = 0) {    const box = el.getBoundingClientRect(),
          top = (box.top >= 0),
          left = (box.left >= 0),
          bottom = (box.bottom <= (window.innerHeight || document.documentElement.clientHeight) + offset),
          right = (box.right <= (window.innerWidth || document.documentElement.clientWidth) + offset);
    return (top && left && bottom && right);
}