我如何知道一个DOM元素在当前视口中是可见的?

是否有一种有效的方法来判断DOM元素(在HTML文档中)当前是否可见(出现在视口中)?

(这个问题指的是Firefox。)

当前回答

这检查元素是否至少部分在视图中(垂直维度):

function inView(element) {
    var box = element.getBoundingClientRect();
    return inViewBox(box);
}

function inViewBox(box) {
    return ((box.bottom < 0) || (box.top > getWindowSize().h)) ? false : true;
}


function getWindowSize() {
    return { w: document.body.offsetWidth || document.documentElement.offsetWidth || window.innerWidth, h: document.body.offsetHeight || document.documentElement.offsetHeight || window.innerHeight}
}

2015-01-02 12:17:33

其他回答

作为公共服务: Dan的答案与正确的计算(元素可以>窗口，特别是在手机屏幕上)，并正确的jQuery测试，以及添加isElementPartiallyInViewport:

顺便说一下，窗户和窗户的区别。innerWidth和document.documentElement.clientWidth是clientWidth/clientHeight不包括滚动条，while窗口。innerWidth /高。

function isElementPartiallyInViewport(el)
{
    // Special bonus for those using jQuery
    if (typeof jQuery !== 'undefined' && el instanceof jQuery) 
        el = el[0];

    var rect = el.getBoundingClientRect();
    // DOMRect { x: 8, y: 8, width: 100, height: 100, top: 8, right: 108, bottom: 108, left: 8 }
    var windowHeight = (window.innerHeight || document.documentElement.clientHeight);
    var windowWidth = (window.innerWidth || document.documentElement.clientWidth);

    // http://stackoverflow.com/questions/325933/determine-whether-two-date-ranges-overlap
    var vertInView = (rect.top <= windowHeight) && ((rect.top + rect.height) >= 0);
    var horInView = (rect.left <= windowWidth) && ((rect.left + rect.width) >= 0);

    return (vertInView && horInView);
}


// http://stackoverflow.com/questions/123999/how-to-tell-if-a-dom-element-is-visible-in-the-current-viewport
function isElementInViewport (el)
{
    // Special bonus for those using jQuery
    if (typeof jQuery !== 'undefined' && el instanceof jQuery) 
        el = el[0];

    var rect = el.getBoundingClientRect();
    var windowHeight = (window.innerHeight || document.documentElement.clientHeight);
    var windowWidth = (window.innerWidth || document.documentElement.clientWidth);

    return (
           (rect.left >= 0)
        && (rect.top >= 0)
        && ((rect.left + rect.width) <= windowWidth)
        && ((rect.top + rect.height) <= windowHeight)
    );
}


function fnIsVis(ele)
{
    var inVpFull = isElementInViewport(ele);
    var inVpPartial = isElementPartiallyInViewport(ele);
    console.clear();
    console.log("Fully in viewport: " + inVpFull);
    console.log("Partially in viewport: " + inVpPartial);
}

测试用例

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="description" content="">
    <meta name="author" content="">
    <title>Test</title>
    <!--
    <script src="http://cdnjs.cloudflare.com/ajax/libs/jquery/1.8.3/jquery.min.js"></script>
    <script src="scrollMonitor.js"></script>
    -->

    <script type="text/javascript">

        function isElementPartiallyInViewport(el)
        {
            // Special bonus for those using jQuery
            if (typeof jQuery !== 'undefined' && el instanceof jQuery) 
                el = el[0];

            var rect = el.getBoundingClientRect();
            // DOMRect { x: 8, y: 8, width: 100, height: 100, top: 8, right: 108, bottom: 108, left: 8 }
            var windowHeight = (window.innerHeight || document.documentElement.clientHeight);
            var windowWidth = (window.innerWidth || document.documentElement.clientWidth);

            // http://stackoverflow.com/questions/325933/determine-whether-two-date-ranges-overlap
            var vertInView = (rect.top <= windowHeight) && ((rect.top + rect.height) >= 0);
            var horInView = (rect.left <= windowWidth) && ((rect.left + rect.width) >= 0);

            return (vertInView && horInView);
        }


        // http://stackoverflow.com/questions/123999/how-to-tell-if-a-dom-element-is-visible-in-the-current-viewport
        function isElementInViewport (el)
        {
            // Special bonus for those using jQuery
            if (typeof jQuery !== 'undefined' && el instanceof jQuery) 
                el = el[0];

            var rect = el.getBoundingClientRect();
            var windowHeight = (window.innerHeight || document.documentElement.clientHeight);
            var windowWidth = (window.innerWidth || document.documentElement.clientWidth);

            return (
                   (rect.left >= 0)
                && (rect.top >= 0)
                && ((rect.left + rect.width) <= windowWidth)
                && ((rect.top + rect.height) <= windowHeight)
            );
        }


        function fnIsVis(ele)
        {
            var inVpFull = isElementInViewport(ele);
            var inVpPartial = isElementPartiallyInViewport(ele);
            console.clear();
            console.log("Fully in viewport: " + inVpFull);
            console.log("Partially in viewport: " + inVpPartial);
        }


        // var scrollLeft = (window.pageXOffset !== undefined) ? window.pageXOffset : (document.documentElement || document.body.parentNode || document.body).scrollLeft,
        // var scrollTop = (window.pageYOffset !== undefined) ? window.pageYOffset : (document.documentElement || document.body.parentNode || document.body).scrollTop;
    </script>
</head>

<body>
    <div style="display: block; width: 2000px; height: 10000px; background-color: green;">

        <br /><br /><br /><br /><br /><br />
        <br /><br /><br /><br /><br /><br />
        <br /><br /><br /><br /><br /><br />

        <input type="button" onclick="fnIsVis(document.getElementById('myele'));" value="det" />

        <br /><br /><br /><br /><br /><br />
        <br /><br /><br /><br /><br /><br />
        <br /><br /><br /><br /><br /><br />

        <div style="background-color: crimson; display: inline-block; width: 800px; height: 500px;" ></div>
        <div id="myele" onclick="fnIsVis(this);" style="display: inline-block; width: 100px; height: 100px; background-color: hotpink;">
        t
        </div>

        <br /><br /><br /><br /><br /><br />
        <br /><br /><br /><br /><br /><br />
        <br /><br /><br /><br /><br /><br />

        <input type="button" onclick="fnIsVis(document.getElementById('myele'));" value="det" />
    </div>

    <!--
    <script type="text/javascript">

        var element = document.getElementById("myele");
        var watcher = scrollMonitor.create(element);

        watcher.lock();

        watcher.stateChange(function() {
            console.log("state changed");
            // $(element).toggleClass('fixed', this.isAboveViewport)
        });
    </script>
    -->
</body>
</html>

2014-09-25 12:54:30

下面是检查给定元素在其父元素中是否完全可见的代码片段:

export const visibleInParentViewport = (el) => {
  const elementRect = el.getBoundingClientRect();
  const parentRect = el.parentNode.getBoundingClientRect();

  return (
    elementRect.top >= parentRect.top &&
    elementRect.right >= parentRect.left &&
    elementRect.top + elementRect.height <= parentRect.bottom &&
    elementRect.left + elementRect.width <= parentRect.right
  );
}

2021-04-16 11:24:37

这里所有的答案都是确定元素是否完全包含在视口中，而不仅仅是以某种方式可见。例如，如果在视图的底部只有图像的一半可见，这里的解决方案将失败，考虑到“外部”。

我有一个用例，我正在通过IntersectionObserver进行惰性加载，但由于弹出过程中发生的动画，我不想观察任何已经在页面加载上交叉的图像。为此，我使用了以下代码:

const bounding = el.getBoundingClientRect();
const isVisible = (0 < bounding.top && bounding.top < (window.innerHeight || document.documentElement.clientHeight)) ||
        (0 < bounding.bottom && bounding.bottom < (window.innerHeight || document.documentElement.clientHeight));

这基本上是检查顶部或底部边界是否在视口中独立。另一端可能在外面，但只要一端在里面，它至少是部分“可见”的。

2020-03-12 03:19:33

新的交集观察者API非常直接地解决了这个问题。

这个解决方案将需要一个polyfill，因为Safari, Opera和Internet Explorer还不支持这个(polyfill包含在解决方案中)。

在这个解决方案中，在视图外有一个框，即目标(观察到的)。当它进入视图时，头部顶部的按钮是隐藏的。一旦框离开视图，就会显示它。

2019-03-15 11:32:46

更新:时间在流逝，我们的浏览器也是如此。这种方法不再被推荐，如果你不需要支持ie7之前的版本，你应该使用Dan的解决方案。

原来的解决方案(现已过时):

这将检查元素是否在当前视口中完全可见:

function elementInViewport(el) {
  var top = el.offsetTop;
  var left = el.offsetLeft;
  var width = el.offsetWidth;
  var height = el.offsetHeight;

  while(el.offsetParent) {
    el = el.offsetParent;
    top += el.offsetTop;
    left += el.offsetLeft;
  }

  return (
    top >= window.pageYOffset &&
    left >= window.pageXOffset &&
    (top + height) <= (window.pageYOffset + window.innerHeight) &&
    (left + width) <= (window.pageXOffset + window.innerWidth)
  );
}

你可以简单地修改它，以确定元素的任何部分在视口中是否可见:

function elementInViewport2(el) {
  var top = el.offsetTop;
  var left = el.offsetLeft;
  var width = el.offsetWidth;
  var height = el.offsetHeight;

  while(el.offsetParent) {
    el = el.offsetParent;
    top += el.offsetTop;
    left += el.offsetLeft;
  }

  return (
    top < (window.pageYOffset + window.innerHeight) &&
    left < (window.pageXOffset + window.innerWidth) &&
    (top + height) > window.pageYOffset &&
    (left + width) > window.pageXOffset
  );
}

2008-09-24 02:40:09

我如何知道一个DOM元素在当前视口中是可见的?

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