jQuery 检查元素是否滚动到顶部
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check if element got scrolled to top
提问by Top Questions
I want to check if an element is scrolled to top with an offset of ~ 100px.
我想检查一个元素是否以 ~ 100px 的偏移量滚动到顶部。
I′ve got a page with 5 subcontents and 2 classes to make backgrounds. It looks like this:
我有一个包含 5 个子内容和 2 个类的页面来制作背景。它看起来像这样：
<div class="background1">
Content1
</div>
<div class="background2">
Content2
</div>
<div class="background1">
Content3
</div>
<div class="background2">
Content4
</div>
<div class="background1">
Content5
</div>
Now i want to check, when one of these classes reaches the top by scrolling
现在我想检查一下，当这些类之一通过滚动到达顶部时
This is one of my last trys:
这是我最后的尝试之一：
$('.background1', '.background2').position(function(){
if($(this).position().top == 100){
alert('checkThis');
}
});
I think this is my closest try by now...of course this code is in document.ready and at the end of my code....
我认为这是我现在最接近的尝试……当然，这段代码在 document.ready 中，并在我的代码末尾……
TLDR: How to check if an element got scrolled to top (and some offset)?
TLDR：如何检查元素是否滚动到顶部（以及一些偏移量）？
回答by adeneo
You have to listen for the scroll event, then check each element against the currently scrolled distance, something like :
您必须监听滚动事件，然后根据当前滚动距离检查每个元素，例如：
$(window).on('scroll', function() {
var scrollTop = $(this).scrollTop();
$('.background1, .background2').each(function() {
var topDistance = $(this).offset().top;
if ( (topDistance+100) < scrollTop ) {
alert( $(this).text() + ' was scrolled to the top' );
}
});
});
