当某个 div 存在时如何隐藏元素？

Question

I want to hide my sticky button when the slider or footer is being in view when scrolled upon.

I tried this code:

$(window).scroll(function() {
    if ($(this).scrollTop() < 250) { 
        $("#sticky-button").css({
            'display': 'none'
        });
    }
});

So what this does is to hide my sticky button when it is below 250px scroll height.

But on mobile, I realise it doesn't work as 250px in mobile is quite a huge height.

So how to do this by making it work upon a certain div (like: #slider, #footer) instead of setting that 250 height?

Answer 1

You should check the element for its position using .offset().top

 $(window).scroll(function() { var elemOffsetTop = $('#slider').offset().top; if ($(this).scrollTop() > elemOffsetTop ) { $("#sticky-button").css({ 'display': 'none' }); }else{ $("#sticky-button").css({ 'display': 'block' }); } });

 #sticky-button{ position: fixed; top:0; left:0; width: 100px; height: 100px; background-color: blue; }.section{ width: 100%; height: 200px; border: 2px solid red; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <div id="sticky-button"></div> <div class="section"></div> <div class="section"></div> <div id="slider" class="section">slider</div> <div class="section"></div> <div class="section"></div> <div class="section"></div>

Answer 2

You can try this

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));
}

if (isScrolledIntoView($('#yourDiv'))) {
    $("#sticky-button").css({
        'display': 'none'
    });
}