将元素移动到屏幕可见范围内

scrollElementIntoView

function scrollElementIntoView(el, offsetTop) {
	var doc = document.documentElement
	var docScrollTop = doc.scrollTop || 0
	var viewportHeight = window.innerHeight
	var rect = el.getBoundingClientRect()
	if (rect.top < 0 || rect.top + rect.height > docScrollTop + viewportHeight) {
		var elOffsetTop = (rect.top + docScrollTop)
		var newScrollTop = elOffsetTop - (offsetTop > 0 ? offsetTop : (rect.height > viewportHeight ? 0 : (viewportHeight - rect.height) / 2))
		doc.scrollTop = newScrollTop
	}
}