Question

我制作了这个jsfiddle：onBackpressureLatest，它可以解释大部分问题。

如果菜单在浮动块内，如何阻止粘性菜单离开包装内部？我尝试了各种各样的js插件，但是那些只能用于相对div而不是浮动我想。包装器使用溢出包围浮动div：hidden;

.item的高度不知道。

HTML：

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<body>
    <div class="header"></div>
    <div class="wrap">
        <div class="content">
            <div class="item">Height of these elements isn't known</div>
            <div class="item">Test test</div>
            <div class="item">Test test</div>
            <div class="item">Test test</div>
        </div>
        <div class="sidebar">
            <div class="menu">
                <div class="menu-top">Top of the menu should stay here</div>
                <div class="menu-bottom">This part of the menu needs to be sticky, but stop at the end of .wrap</div>
            </div>
        </div>
    </div>
    <div class="footer"></div>
</body>

JS：

$(document).ready(function(){
    // to set the width right even when position is fixed
    var divWidth = $('.sidebar').width(); 
    $('.menu-bottom').css('width', divWidth+'px');


    var fixmeTop2 = $('.menu-bottom').offset().top;
    $(window).scroll(function() {
        var currentScroll2 = $(window).scrollTop();
        if (currentScroll2 >= fixmeTop2) {
            $('.menu-bottom').css({
                position: 'fixed',
                top: '20px'      
            });
        } else {
            $('.menu-bottom').css({
                position: 'relative'
        });
    }
});
});

CSS：

body {
    margin: 0;
    padding: 0;
    font-size: 16px;
}

.wrap, .footer, .header {
    position: relative;
    width: 75%;
    margin: auto;
    overflow: hidden;
    background-color: #EBEBEB;
}

.footer, .header {
    height: 200px;
    background-color: #999;
}

.footer {
    height: 2000px;
}

.content {
    float: left;
    position: relative;
    width: 70%;
}

.sidebar {
    float: left;    
    position: relative;
    width: 30%;
    background-color: #0CF;
}

.item {
    height: 300px;
    position: relative;
    width: 100%;
    background-color: #0F6;
    margin-bottom: 20px;
    box-sizing: border-box;
    padding: 20px;
}

.menu-top {
    height: 120px;  
    box-sizing: border-box;
    padding: 20px;
}

.menu-bottom {
    z-index: 99;
    position: relative;
    height: 300px;
    background-color: red;  
    box-sizing: border-box;
    padding: 20px;
}

Answer 1

进行了一些优化，切换了额外的sticky类。使用smoothscroll和各种填充边距检查Firefox并且似乎对确切位置做出响应：

Demo

.sticky {
position: fixed;
}

$(function() {

var wrap = $('.wrap'),
lowmenu = $('.menu-bottom'),
range = $('.sidebar').width(),
fromtop = 60,
edge = parseInt($('.item:last').css('margin-bottom'));

lowmenu.css('width', range);

var fixtop = lowmenu.offset().top-fromtop,
lowpoint = wrap.offset().top+wrap.outerHeight()-lowmenu.outerHeight()-edge-fromtop,
placetop = wrap.outerHeight()-lowmenu.outerHeight()-$('.menu-top').outerHeight()-edge;

$(window).scroll(function() {

    var current = $(window).scrollTop();

    if (current >= fixtop && current <= lowpoint && !stuck()) lowmenu.addClass('sticky').css('top', fromtop);
    else if (current > lowpoint && stuck()) lowmenu.removeClass('sticky').css('top', placetop);
    else if (current < fixtop && stuck()) lowmenu.removeClass('sticky').css('top', 0);;
    });

function stuck() {

    return lowmenu.hasClass('sticky');
}
});

您可以将fromtop设置为任意数字。最后.item的保证金也应计入......

如何在浮动侧边栏中保留粘性菜单？

1 个答案: