我正在通过AJAX加载元素 . 只有向下滚动页面时，其中一些才可见 .
有什么方法我可以知道元素现在是否在页面的可见部分？

30 回答

这是我的纯JavaScript解决方案，如果它也隐藏在可滚动容器中，它也可以工作 .

Demo here（尝试调整窗口大小）

var visibleY = function(el){
  var rect = el.getBoundingClientRect(), top = rect.top, height = rect.height, 
    el = el.parentNode
  // Check if bottom of the element is off the page
  if (rect.bottom < 0) return false
  // Check its within the document viewport
  if (top > document.documentElement.clientHeight) return false
  do {
    rect = el.getBoundingClientRect()
    if (top <= rect.bottom === false) return false
    // Check if the element is out of view due to a container scrolling
    if ((top + height) <= rect.top) return false
    el = el.parentNode
  } while (el != document.body)
  return true
};

编辑2016-03-26：我've updated the solution to account for scrolling past the element so it'隐藏在可滚动容器的顶部之上 . 编辑2018-10-08：更新以在屏幕上方滚动视图时进行处理 .

回复于 2024-05-02T15:50:37+08:00

我需要检查可滚动DIV容器内元素的可见性

//p = DIV container scrollable
    //e = element
    function visible_in_container(p, e) {
        var z = p.getBoundingClientRect();
        var r = e.getBoundingClientRect();

        // Check style visiblilty and off-limits
        return e.style.opacity > 0 && e.style.display !== 'none' &&
               e.style.visibility !== 'hidden' &&
               !(r.top > z.bottom || r.bottom < z.top ||
                 r.left > z.right || r.right < z.left);
    }

回复于 2024-05-02T15:50:37+08:00

我更喜欢使用jQuery expr

jQuery.extend(jQuery.expr[':'], {  
    inview: function (elem) {
        var t = $(elem);
        var offset = t.offset();
        var win = $(window); 
        var winST = win.scrollTop();
        var elHeight = t.outerHeight(true);

        if ( offset.top > winST - elHeight && offset.top < winST + elHeight + win.height()) {
            return true;    
        }    
        return false;  
    }
});

所以你可以这样使用它

$(".my-elem:inview"); //returns only element that is in view
$(".my-elem").is(":inview"); //check if element is in view
$(".my-elem:inview").length; //check how many elements are in view

您可以在 scroll 事件函数等中轻松添加此类代码，以便每次用户滚动视图时进行检查 .

回复于 2024-05-02T15:50:37+08:00

9
jQuery Waypoints插件在这里非常好用 .
```
$('.entry').waypoint(function() {
   alert('You have scrolled to an entry.');
});
```
site of the plugin上有一些例子 .
回复于 2024-05-02T15:50:37+08:00

使用（“new”）IntersectionObserver API

确定视口中是否有可见元素非常简单有效 . 通过使用观察者，它消除了附加 scroll 事件和手动检查事件回调的需要 .

// this is the target which is observed
var target = document.querySelector('div');

// configure the intersection observer instance
var intersectionObserverOptions = {
  root: null,
  rootMargin: '150px',
  threshold: 1.0
}
    
var observer = new IntersectionObserver(onIntersection, intersectionObserverOptions);

// provice the observer with a target
observer.observe(target);

function onIntersection(entries){
  entries.forEach(entry => {
    console.clear();
    console.log(entry.intersectionRatio)
    target.classList.toggle('visible', entry.intersectionRatio > 0);
    
    // Are we in viewport?
    if (entry.intersectionRatio > 0) {
      // Stop watching 
      // observer.unobserve(entry.target);
    }
  });
}

.box{ width:100px; height:100px; background:red; margin:1000px; }
.box.visible{ background:green; }

Scroll both Vertically & Horizontally...
<div class='box'></div>

查看浏览器支持表（IE / Safari不支持）

回复于 2024-05-02T15:50:37+08:00

1153

WebResourcesDepot写了a script to load while scrolling，前一段时间使用jQuery . 你可以查看他们的Live Demo Here . 他们功能的牛肉是这样的：

$(window).scroll(function(){
  if  ($(window).scrollTop() == $(document).height() - $(window).height()){
    lastAddedLiveFunc();
  }
});

function lastAddedLiveFunc() { 
  $('div#lastPostsLoader').html('<img src="images/bigLoader.gif">');
  $.post("default.asp?action=getLastPosts&lastPostID="+$(".wrdLatest:last").attr("id"),
    function(data){
        if (data != "") {
          $(".wrdLatest:last").after(data);         
        }
      $('div#lastPostsLoader').empty();
    });
};

回复于 2024-05-02T15:50:37+08:00

基于this answer的示例，用于检查元素是否可见75％（即，其中少于25％的元素离开屏幕） .

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;
}

回复于 2024-05-02T15:50:37+08:00

这会考虑元素具有的任何填充，边框或边距以及大于视口本身的元素 .

function inViewport($ele) {
    var lBound = $(window).scrollTop(),
        uBound = lBound + $(window).height(),
        top = $ele.offset().top,
        bottom = top + $ele.outerHeight(true);

    return (top > lBound && top < uBound)
        || (bottom > lBound && bottom < uBound)
        || (lBound >= top && lBound <= bottom)
        || (uBound >= top && uBound <= bottom);
}

要调用它，请使用以下内容：

var $myElement = $('#my-element'),
    canUserSeeIt = inViewport($myElement);

console.log(canUserSeeIt); // true, if element is visible; false otherwise

回复于 2024-05-02T15:50:37+08:00

Build this great answer，您可以使用ES2015进一步简化它：

function isScrolledIntoView(el) {
  const { top, bottom } = el.getBoundingClientRect()
  return top >= 0 && bottom <= window.innerHeight
}

如果您不关心顶部窗外，只关心底部已被查看，这可以简化为

function isSeen(el) {
  return el.getBoundingClientRect().bottom <= window.innerHeight
}

甚至是单行班轮

const isSeen = el => el.getBoundingClientRect().bottom <= window.innerHeight

回复于 2024-05-02T15:50:37+08:00

115

普通香草检查元素（ el ）是否在可滚动div中可见（ holder ）

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
},

用于jQuery：

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

回复于 2024-05-02T15:50:37+08:00

2

我已经为这项任务编写了a component，旨在处理大量元素extremely fast（在慢速移动设备上为1000个元素调整<10ms） .

它适用于您可以访问的每种类型的滚动容器 - 窗口，HTML元素，嵌入式iframe，衍生的子窗口 - 并且在检测到的内容方面非常灵活（full or partial visibility，border box or content box，custom tolerance zone，etc） .

一个巨大的，主要是自动生成的测试套件可确保它像宣传的那样工作，cross-browser .

如果你愿意，可以试一试：jQuery.isInView . 否则，您可能会在源代码中找到灵感，例如： here .

回复于 2024-05-02T15:50:37+08:00

This answer在香草：

function isScrolledIntoView(el) {
    var rect = el.getBoundingClientRect();
    var elemTop = rect.top;
    var elemBottom = rect.bottom;

    // Only completely visible elements return true:
    var isVisible = (elemTop >= 0) && (elemBottom <= window.innerHeight);
    // Partially visible elements return true:
    //isVisible = elemTop < window.innerHeight && elemBottom >= 0;
    return isVisible;
}

回复于 2024-05-02T15:50:37+08:00

这是http://web-profile.com.ua/的另一个解决方案

<script type="text/javascript">
$.fn.is_on_screen = function(){
    var win = $(window);
    var viewport = {
        top : win.scrollTop(),
        left : win.scrollLeft()
    };
    viewport.right = viewport.left + win.width();
    viewport.bottom = viewport.top + win.height();

    var bounds = this.offset();
    bounds.right = bounds.left + this.outerWidth();
    bounds.bottom = bounds.top + this.outerHeight();

    return (!(viewport.right < bounds.left || viewport.left > bounds.right ||    viewport.bottom < bounds.top || viewport.top > bounds.bottom));
 };

if( $('.target').length > 0 ) { // if target element exists in DOM
    if( $('.target').is_on_screen() ) { // if target element is visible on screen after DOM loaded
        $('.log').html('<div class="alert alert-success">target element is visible on screen</div>'); // log info       
    } else {
        $('.log').html('<div class="alert">target element is not visible on screen</div>'); // log info
    }
}
$(window).scroll(function(){ // bind window scroll event
if( $('.target').length > 0 ) { // if target element exists in DOM
    if( $('.target').is_on_screen() ) { // if target element is visible on screen after DOM loaded
        $('.log').html('<div class="alert alert-success">target element is visible on screen</div>'); // log info
    } else {
        $('.log').html('<div class="alert">target element is not visible on screen</div>'); // log info
    }
}
});
</script>

在JSFiddle中看到它

回复于 2024-05-02T15:50:37+08:00

我改编了这个简短的jQuery函数扩展，您可以随意使用（MIT许可证） .

/**
 * returns true if an element is visible, with decent performance
 * @param [scope] scope of the render-window instance; default: window
 * @returns {boolean}
 */
jQuery.fn.isOnScreen = function(scope){
    var element = this;
    if(!element){
        return;
    }
    var target = $(element);
    if(target.is(':visible') == false){
        return false;
    }
    scope = $(scope || window);
    var top = scope.scrollTop();
    var bot = top + scope.height();
    var elTop = target.offset().top;
    var elBot = elTop + target.height();

    return ((elBot <= bot) && (elTop >= top));
};

回复于 2024-05-02T15:50:37+08:00

怎么样

function isInView(elem){
   return $(elem).offset().top - $(window).scrollTop() < $(elem).height() ;
}

之后，一旦元素在视图中，你可以触发你想要的任何东西

$(window).scroll(function(){
   if (isInView($('.classOfDivToCheck')))
      //fire whatever you what 
      dothis();
})

这对我很有用

回复于 2024-05-02T15:50:37+08:00

这里的大多数答案没有考虑到元素也可以被隐藏，因为它被滚动到div的视图之外，而不仅仅是整个页面的视图 .

为了覆盖这种可能性，您基本上必须检查元素是否位于其每个父项的边界内 .

这个解决方案正是如此：

function(element, percentX, percentY){
    var tolerance = 0.01;   //needed because the rects returned by getBoundingClientRect provide the position up to 10 decimals
    if(percentX == null){
        percentX = 100;
    }
    if(percentY == null){
        percentY = 100;
    }

    var elementRect = element.getBoundingClientRect();
    var parentRects = [];

    while(element.parentElement != null){
        parentRects.push(element.parentElement.getBoundingClientRect());
        element = element.parentElement;
    }

    var visibleInAllParents = parentRects.every(function(parentRect){
        var visiblePixelX = Math.min(elementRect.right, parentRect.right) - Math.max(elementRect.left, parentRect.left);
        var visiblePixelY = Math.min(elementRect.bottom, parentRect.bottom) - Math.max(elementRect.top, parentRect.top);
        var visiblePercentageX = visiblePixelX / elementRect.width * 100;
        var visiblePercentageY = visiblePixelY / elementRect.height * 100;
        return visiblePercentageX + tolerance > percentX && visiblePercentageY + tolerance > percentY;
    });
    return visibleInAllParents;
};

它还允许您指定在每个方向上可见的百分比 .
它没有涵盖由于其他因素而可能被隐藏的可能性，例如 display: hidden .

这应该适用于所有主流浏览器，因为它只使用getBoundingClientRect . 我亲自在Chrome和Internet Explorer 11中测试过它 .

回复于 2024-05-02T15:50:37+08:00

如果你想调整这个在另一个div中滚动项目，

function isScrolledIntoView (elem, divID) 

{

    var docViewTop = $('#' + divID).scrollTop();


    var docViewBottom = docViewTop + $('#' + divID).height();

    var elemTop = $(elem).offset().top;
    var elemBottom = elemTop + $(elem).height();

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

回复于 2024-05-02T15:50:37+08:00

可滚动div（容器）的简单修改

var isScrolledIntoView = function(elem, container) {
    var containerHeight = $(container).height();
    var elemTop = $(elem).position().top;
    var elemBottom = elemTop + $(elem).height();
    return (elemBottom > 0 && elemTop < containerHeight);
}

注意：如果元素大于可滚动div，则此方法无效 .

回复于 2024-05-02T15:50:37+08:00

这是一种使用Mootools在水平，垂直或两者中实现相同功能的方法 .

Element.implement({
inVerticalView: function (full) {
    if (typeOf(full) === "null") {
        full = true;
    }

    if (this.getStyle('display') === 'none') {
        return false;
    }

    // Window Size and Scroll
    var windowScroll = window.getScroll();
    var windowSize = window.getSize();
    // Element Size and Scroll
    var elementPosition = this.getPosition();
    var elementSize = this.getSize();

    // Calculation Variables
    var docViewTop = windowScroll.y;
    var docViewBottom = docViewTop + windowSize.y;
    var elemTop = elementPosition.y;
    var elemBottom = elemTop + elementSize.y;

    if (full) {
        return ((elemBottom >= docViewTop) && (elemTop <= docViewBottom)
            && (elemBottom <= docViewBottom) && (elemTop >= docViewTop) );
    } else {
        return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
    }
},
inHorizontalView: function(full) {
    if (typeOf(full) === "null") {
        full = true;
    }

    if (this.getStyle('display') === 'none') {
        return false;
    }

    // Window Size and Scroll
    var windowScroll = window.getScroll();
    var windowSize = window.getSize();
    // Element Size and Scroll
    var elementPosition = this.getPosition();
    var elementSize = this.getSize();

    // Calculation Variables
    var docViewLeft = windowScroll.x;
    var docViewRight = docViewLeft + windowSize.x;
    var elemLeft = elementPosition.x;
    var elemRight = elemLeft + elementSize.x;

    if (full) {
        return ((elemRight >= docViewLeft) && (elemLeft <= docViewRight)
            && (elemRight <= docViewRight) && (elemLeft >= docViewLeft) );
    } else {
        return ((elemRight <= docViewRight) && (elemLeft >= docViewLeft));
    }
},
inView: function(full) {
    return this.inHorizontalView(full) && this.inVerticalView(full);
}});

回复于 2024-05-02T15:50:37+08:00

我的应用程序中有这样的方法，但它不使用jQuery：

/* Get the TOP position of a given element. */
function getPositionTop(element){
    var offset = 0;
    while(element) {
        offset += element["offsetTop"];
        element = element.offsetParent;
    }
    return offset;
}

/* Is a given element is visible or not? */
function isElementVisible(eltId) {
    var elt = document.getElementById(eltId);
    if (!elt) {
        // Element not found.
        return false;
    }
    // Get the top and bottom position of the given element.
    var posTop = getPositionTop(elt);
    var posBottom = posTop + elt.offsetHeight;
    // Get the top and bottom position of the *visible* part of the window.
    var visibleTop = document.body.scrollTop;
    var visibleBottom = visibleTop + document.documentElement.offsetHeight;
    return ((posBottom >= visibleTop) && (posTop <= visibleBottom));
}

编辑：这种方法适用于I.E. （至少版本6） . 阅读注释以了解与FF的兼容性 .

回复于 2024-05-02T15:50:37+08:00

2

到目前为止我找到的最好的方法是jQuery appear plugin . 奇迹般有效 .

模仿自定义“出现”事件，当元素滚动到视图中或以其他方式对用户可见时触发 . $（'＃foo'） . 出现（function（）{
$（this）.text（'Hello world'）;
}）;
此插件可用于防止对隐藏或可视区域外的内容进行不必要的请求 .

回复于 2024-05-02T15:50:37+08:00

您可以使用jquery插件"onScreen"来滚动时检查元素是否在当前视口中 . 当选择器出现在屏幕上时，插件将选择器的":onScreen"设置为true . 这是插件的链接您可以在项目中包含哪些内容 . “http://benpickles.github.io/onScreen/jquery.onscreen.min.js”

您可以尝试以下适用于我的示例 .

$(document).scroll(function() {
    if($("#div2").is(':onScreen')) {
        console.log("Element appeared on Screen");
        //do all your stuffs here when element is visible.
    }
    else {
        console.log("Element not on Screen");
        //do all your stuffs here when element is not visible.
    }
});

HTML代码：

<div id="div1" style="width: 400px; height: 1000px; padding-top: 20px; position: relative; top: 45px"></div> <br>
<hr /> <br>
<div id="div2" style="width: 400px; height: 200px"></div>

CSS：

#div1 {
    background-color: red;
}
#div2 {
    background-color: green;
}

回复于 2024-05-02T15:50:37+08:00

314

我正在寻找一种方法来查看该元素是否即将进入视图，因此通过扩展上面的片段，我设法做到了 . 以为我会留在这里以防万一它会帮助别人

elm =是您要检查的元素在视图中

scrollElement =您可以传递 window 或具有滚动的父元素

offset =如果你希望它在元素在屏幕之前200px之前触发，然后传递200

function isScrolledIntoView(elem, scrollElement, offset)
        {
            var $elem = $(elem);
            var $window = $(scrollElement);
            var docViewTop = $window.scrollTop();
            var docViewBottom = docViewTop + $window.height();
            var elemTop = $elem.offset().top;
            var elemBottom = elemTop + $elem.height();
            
            return (((elemBottom+offset) >= docViewBottom) && ((elemTop-offset) <= docViewTop)) || (((elemBottom-offset) <= docViewBottom) && ((elemTop+offset) >= docViewTop));
        }

回复于 2024-05-02T15:50:37+08:00

function isScrolledIntoView(elem) {
    var docViewTop = $(window).scrollTop(),
        docViewBottom = docViewTop + $(window).height(),
        elemTop = $(elem).offset().top,
     elemBottom = elemTop + $(elem).height();
   //Is more than half of the element visible
   return ((elemTop + ((elemBottom - elemTop)/2)) >= docViewTop && ((elemTop + ((elemBottom - elemTop)/2)) <= docViewBottom));
}

回复于 2024-05-02T15:50:37+08:00

如果元素的任何部分在页面上可见，则此方法将返回true . 它在我的情况下效果更好，可能会帮助别人 .

function isOnScreen(element) {
  var elementOffsetTop = element.offset().top;
  var elementHeight = element.height();

  var screenScrollTop = $(window).scrollTop();
  var screenHeight = $(window).height();

  var scrollIsAboveElement = elementOffsetTop + elementHeight - screenScrollTop >= 0;
  var elementIsVisibleOnScreen = screenScrollTop + screenHeight - elementOffsetTop >= 0;

  return scrollIsAboveElement && elementIsVisibleOnScreen;
}

回复于 2024-05-02T15:50:37+08:00

修改了已接受的答案，以便元素必须将其显示属性设置为“无”以外的其他内容，以使质量可见 .

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);
}

回复于 2024-05-02T15:50:37+08:00

这应该是诀窍：

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

    var elemTop = $(elem).offset().top;
    var elemBottom = elemTop + $(elem).height();

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

Simple Utility Function 这将允许您调用一个实用程序函数，该函数接受您正在查找的元素，以及您希望元素完全在视图中还是部分在视图中 .

function Utils() {

}

Utils.prototype = {
    constructor: Utils,
    isElementInView: function (element, fullyInView) {
        var pageTop = $(window).scrollTop();
        var pageBottom = pageTop + $(window).height();
        var elementTop = $(element).offset().top;
        var elementBottom = elementTop + $(element).height();

        if (fullyInView === true) {
            return ((pageTop < elementTop) && (pageBottom > elementBottom));
        } else {
            return ((elementTop <= pageBottom) && (elementBottom >= pageTop));
        }
    }
};

var Utils = new Utils();

Usage

var isElementInView = Utils.isElementInView($('#flyout-left-container'), false);

if (isElementInView) {
    console.log('in view');
} else {
    console.log('out of view');
}

回复于 2024-05-02T15:50:37+08:00

2
isScrolledIntoView 是一个非常需要的函数，所以我尝试了它，它适用于不比视口更高的元素，但如果元素比视口更大则不起作用 . 要解决此问题，请轻松更改条件
```
return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
```
对此：
```
return (docViewBottom >= elemTop && docViewTop <= elemBottom);
```
在这里看演示：http://jsfiddle.net/RRSmQ/
回复于 2024-05-02T15:50:37+08:00

根据我的要求推荐了Scott Dowding的酷功能 - 这用于查找元素是否刚刚滚动到屏幕中，即它的顶部边缘 .

function isScrolledIntoView(elem)
{
    var docViewTop = $(window).scrollTop();
    var docViewBottom = docViewTop + $(window).height();
    var elemTop = $(elem).offset().top;
    return ((elemTop <= docViewBottom) && (elemTop >= docViewTop));
}

回复于 2024-05-02T15:50:37+08:00

有一个plugin for jQuery called inview会添加一个新的"inview"事件 .

以下是一些不使用事件的jQuery插件的代码：

$.extend($.expr[':'],{
    inView: function(a) {
        var st = (document.documentElement.scrollTop || document.body.scrollTop),
            ot = $(a).offset().top,
            wh = (window.innerHeight && window.innerHeight < $(window).height()) ? window.innerHeight : $(window).height();
        return ot > st && ($(a).height() + ot) < (st + wh);
    }
});

(function( $ ) {
    $.fn.inView = function() {
        var st = (document.documentElement.scrollTop || document.body.scrollTop),
        ot = $(this).offset().top,
        wh = (window.innerHeight && window.innerHeight < $(window).height()) ? window.innerHeight : $(window).height();

        return ot > st && ($(this).height() + ot) < (st + wh);
    };
})( jQuery );

我在一个名叫詹姆斯的家伙的评论中发现了这个（http://remysharp.com/2009/01/26/element-in-view-event-plugin/）

回复于 2024-05-02T15:50:37+08:00

滚动后检查元素是否可见

30 回答

使用（“new”）IntersectionObserver API

查看浏览器支持表（IE / Safari不支持）

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