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

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

其他回答

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

/**
 * Returns Element placement information in Viewport
 * @link https://stackoverflow.com/a/70476497/2453148
 *
 * @typedef {object} ViewportInfo - Whether the element is…
 * @property {boolean} isInViewport - fully or partially in the viewport
 * @property {boolean} isPartiallyInViewport - partially in the viewport
 * @property {boolean} isInsideViewport - fully inside viewport
 * @property {boolean} isAroundViewport - completely covers the viewport
 * @property {boolean} isOnEdge - intersects the edge of viewport
 * @property {boolean} isOnTopEdge - intersects the top edge
 * @property {boolean} isOnRightEdge - intersects the right edge
 * @property {boolean} isOnBottomEdge - is intersects the bottom edge
 * @property {boolean} isOnLeftEdge - is intersects the left edge
 *
 * @param el Element
 * @return {Object} ViewportInfo
 */
function getElementViewportInfo(el) {

    let result = {};

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

    let insideX = rect.left >= 0 && rect.left + rect.width <= windowWidth;
    let insideY = rect.top >= 0 && rect.top + rect.height <= windowHeight;

    result.isInsideViewport = insideX && insideY;

    let aroundX = rect.left < 0 && rect.left + rect.width > windowWidth;
    let aroundY = rect.top < 0 && rect.top + rect.height > windowHeight;

    result.isAroundViewport = aroundX && aroundY;

    let onTop    = rect.top < 0 && rect.top + rect.height > 0;
    let onRight  = rect.left < windowWidth && rect.left + rect.width > windowWidth;
    let onLeft   = rect.left < 0 && rect.left + rect.width > 0;
    let onBottom = rect.top < windowHeight && rect.top + rect.height > windowHeight;

    let onY = insideY || aroundY || onTop || onBottom;
    let onX = insideX || aroundX || onLeft || onRight;

    result.isOnTopEdge    = onTop && onX;
    result.isOnRightEdge  = onRight && onY;
    result.isOnBottomEdge = onBottom && onX;
    result.isOnLeftEdge   = onLeft && onY;

    result.isOnEdge = result.isOnLeftEdge || result.isOnRightEdge ||
        result.isOnTopEdge || result.isOnBottomEdge;

    let isInX =
        insideX || aroundX || result.isOnLeftEdge || result.isOnRightEdge;
    let isInY =
        insideY || aroundY || result.isOnTopEdge || result.isOnBottomEdge;

    result.isInViewport = isInX && isInY;

    result.isPartiallyInViewport =
        result.isInViewport && result.isOnEdge;

    return result;
}

2021-12-24 21:04:37

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

在我看来，非常简单:

function isVisible(elem) {
  var coords = elem.getBoundingClientRect();
  return Math.abs(coords.top) <= coords.height;
}

2019-03-15 14:06:44

这是我的解决方案。如果一个元素隐藏在一个可滚动的容器中，它将工作。

这里是一个演示(尝试调整窗口大小为)

var visibleY = function(el){
    var top = el.getBoundingClientRect().top, rect, el = el.parentNode;
    do {
        rect = el.getBoundingClientRect();
        if (top <= rect.bottom === false)
            return false;
        el = el.parentNode;
    } while (el != document.body);
    // Check it's within the document viewport
    return top <= document.documentElement.clientHeight;
};

我只需要检查它在Y轴上是否可见(用于滚动Ajax加载更多记录功能)。

2014-02-07 11:39:43

我如何知道一个DOM元素在当前视口中是可见的?

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