简单的检查元素(el)是否在可滚动的div (holder)中可见

function isElementVisible (el, holder) {
  holder = holder || document.body
  const { top, bottom, height } = el.getBoundingClientRect()
  const holderRect = holder.getBoundingClientRect()

  return top <= holderRect.top
    ? holderRect.top - top <= height
    : bottom - holderRect.bottom <= height
}

使用jQuery:

var el = $('tr:last').get(0);
var holder = $('table').get(0);
var isVisible = isElementVisible(el, holder);

仅限Javascript:)

function isInViewport(element) {
  var rect = element.getBoundingClientRect();
  var html = document.documentElement;
  return (
    rect.top >= 0 &&
    rect.left >= 0 &&
    rect.bottom <= (window.innerHeight || html.clientHeight) &&
    rect.right <= (window.innerWidth || html.clientWidth)
  );
}

一个基于这个答案的例子，检查一个元素是否有75%可见(即小于25%的元素在屏幕之外)。

function isScrolledIntoView(el) {
  // check for 75% visible
  var percentVisible = 0.75;
  var elemTop = el.getBoundingClientRect().top;
  var elemBottom = el.getBoundingClientRect().bottom;
  var elemHeight = el.getBoundingClientRect().height;
  var overhang = elemHeight * (1 - percentVisible);

  var isVisible = (elemTop >= -overhang) && (elemBottom <= window.innerHeight + overhang);
  return isVisible;
}

修改了已接受的答案，以便元素必须将其display属性设置为“none”以外的值，以便质量为可见。

function isScrolledIntoView(elem) {
   var docViewTop = $(window).scrollTop();
  var docViewBottom = docViewTop + $(window).height();

  var elemTop = $(elem).offset().top;
  var elemBottom = elemTop + $(elem).height();
  var elemDisplayNotNone = $(elem).css("display") !== "none";

  return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop) && elemDisplayNotNone);
}

检查元素是否在屏幕上，而不是公认的检查div是否完全在屏幕上的方法(如果div比屏幕大，这将不起作用)。在纯Javascript中:

/**
 * Checks if element is on the screen (Y axis only), returning true
 * even if the element is only partially on screen.
 *
 * @param element
 * @returns {boolean}
 */
function isOnScreenY(element) {
    var screen_top_position = window.scrollY;
    var screen_bottom_position = screen_top_position + window.innerHeight;

    var element_top_position = element.offsetTop;
    var element_bottom_position = element_top_position + element.offsetHeight;

    return (inRange(element_top_position, screen_top_position, screen_bottom_position)
    || inRange(element_bottom_position, screen_top_position, screen_bottom_position));
}

/**
 * Checks if x is in range (in-between) the
 * value of a and b (in that order). Also returns true
 * if equal to either value.
 *
 * @param x
 * @param a
 * @param b
 * @returns {boolean}
 */
function inRange(x, a, b) {
    return (x >= a && x <= b);
}

唯一的插件一直为我做这件事，是:https://github.com/customd/jquery-visible

我最近将这个插件移植到GWT，因为我不想仅仅为了使用这个插件而添加jquery作为依赖。下面是我的(简单的)端口(只包括我用例所需的功能):

public static boolean isVisible(Element e)
{
    //vp = viewPort, b = bottom, l = left, t = top, r = right
    int vpWidth   = Window.getClientWidth();
    int vpHeight = Window.getClientHeight();


    boolean tViz = ( e.getAbsoluteTop() >= 0 && e.getAbsoluteTop()<  vpHeight);
    boolean bViz = (e.getAbsoluteBottom() >  0 && e.getAbsoluteBottom() <= vpHeight);
    boolean lViz = (e.getAbsoluteLeft() >= 0 && e.getAbsoluteLeft() < vpWidth);
    boolean rViz = (e.getAbsoluteRight()  >  0 && e.getAbsoluteRight()  <= vpWidth);

    boolean vVisible   = tViz && bViz;
    boolean hVisible   = lViz && rViz;

    return hVisible && vVisible;
}