04月27th
JS判断滚动条到底部
前端设计1424℃我来说两句!
判断滚动条到底部,需要用到DOM的三个属性值,即scrollTop、clientHeight、scrollHeight。scrollTop为滚动条在Y轴上的滚动距离。clientHeight为内容可视区域的高度。scrollHeight为内容可视区域的高度加上溢出(滚动)的距离。
从这个三个属性的介绍就可以看出来,滚动条到底部的条件即为scrollTop + clientHeight == scrollHeight
代码如下(兼容不同的浏览器)。
//滚动条在Y轴上的滚动距离function getScrollTop(){ var scrollTop = 0, bodyScrollTop = 0, documentScrollTop = 0; if(document.body){ bodyScrollTop = document.body.scrollTop; } if(document.documentElement){ documentScrollTop = document.documentElement.scrollTop; } scrollTop = (bodyScrollTop - documentScrollTop > 0) ? bodyScrollTop : documentScrollTop; return scrollTop;}//文档的总高度function getScrollHeight(){ var scrollHeight = 0, bodyScrollHeight = 0, documentScrollHeight = 0; if(document.body){ bodyScrollHeight = document.body.scrollHeight; } if(document.documentElement){ documentScrollHeight = document.documentElement.scrollHeight; } scrollHeight = (bodyScrollHeight - documentScrollHeight > 0) ? bodyScrollHeight : documentScrollHeight; return scrollHeight;}//浏览器视口的高度function getWindowHeight(){ var windowHeight = 0; if(document.compatMode == "CSS1Compat"){ windowHeight = document.documentElement.clientHeight; }else{ windowHeight = document.body.clientHeight; } return windowHeight;}window.onscroll = function(){ if(getScrollTop() + getWindowHeight() == getScrollHeight()){ alert("已经到最底部了!!"); }};
如果用jquery来实现的话就更简单了,
$(window).scroll(function(){
var scrollTop = $(this).scrollTop();
var scrollHeight = $(document).height();
var windowHeight = $(this).height();
if(scrollTop + windowHeight == scrollHeight){
alert("已经到最底部了!");
}
});
如果要判断在某一个元素中的滚动条是否到底部,根据类似的思想,将document.body换成特定的元素即可,获取scrollTop和scrollHeight的方式是一样的,但是获取元素可见高度需要用到offsetHeight属性,直接依葫芦画瓢即可。
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