当用户滚动页面并在其底部有一个箭头时，我想在屏幕上从页面顶部到底部绘制一条线。我不想使用固定位置，以便它始终在同一个位置，我希望它通过确定页面长度等来指示它们在页面上的位置。
我有以下代码可以解决问题。这个问题是当我在中途向下滚动后，箭头从页面底部消失。
我尝试过这段代码的不同变体，但都没有用。有人可以帮忙吗？
//Draw dotted line on scroll - works to certain extent but scrolls off page
$( window ).scroll(function() {
if ( $.windowScrollTop() > 10 ) {
var pos = $.windowScrollTop();
var scrollHeight = $(window).innerHeight();
var element = $('#dashes');
$( '#line' ).css( 'height', pos - scrollHeight / 4 );
$( '#arrow' ).css( 'top', pos - scrollHeight / 4 );
} else {
$( '#line' ).css( 'height', '6px' );
$( '#arrow' ).css( 'top', '-150px' );
}
});
//also tried the below
$(window).on("scroll", function() {
var scrollHeight = $(document).height();
var scrollPosition = $(window).height() + $(window).scrollTop();
if ((scrollHeight - scrollPosition) / scrollHeight === 0) {
// when scroll to bottom of the page
alert('bottom');
} else {
$( '#line' ).css( 'height', $(window).scrollTop() );
$( '#arrow' ).css( 'top', $(window).scrollTop() );
}
});
我们在这里要做的是将文档高度反映到窗口高度的元素中。所以实际的可滚动文档高度将是
var actualScrollHeight = $(document).height() - $(window).height();
/* This is the distance we actually scroll */
而我们的 #line 将具有最大可能的高度
var lineMaxHeight = $(window).height() - topMargin - bottomMargin - arrowHeight;
/* #arrow is inside #line but we positioned it outside it's height */
不反映滚动进度 #line 元素高度我们需要做的是
var lineHeight = $(document).scrollTop() / actualScrollHeight * lineMaxHeight;
/* Super Easy, isn't it? */
最终结果：
你不需要同时定位 #line 和 #arrow。修复 #arrow 在底部 #line 然后只是改变高度 #line 工作得很好。我加了 topMargin 和 bottomMargin 功能使屏幕调整更加自定义。
$(function(){
var topMargin = 15, bottomMargin = 5;
var arrowHeight = $('#arrow').height();
var $lineElement = $('#line');
$lineElement.height(topMargin);
$(window).scroll(function() {
var winHeight = $(window).height();
var actualScrollHeight = $(document).height() - winHeight;
var lineMaxHeight = winHeight - topMargin - bottomMargin - arrowHeight;
var scrollTop = $(document).scrollTop();
var lineHeight = scrollTop / actualScrollHeight * lineMaxHeight;
$lineElement.height(topMargin + lineHeight);
});
});
#logo {
width: 80px;
background-color: #53befd;
padding: 20px;
}
#line {
background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAYAAAAMCAYAAABBV8wuAAAAFklEQVR42mNgoB74OEXzPzY8sBLUAwB6PmBV1D+CIAAAAABJRU5ErkJggg==);
position: fixed;
top: 0px;
right: 19px;
z-index: 20;
width: 3px;
}
#arrow {
background-color: #f28323;
height: 40px;
width: 40px;
position: absolute;
bottom: -40px;
left: -18px;
border-radius: 20px;
color: white;
text-align: center;
font-size: 32px;
line-height: 35px;
padding-top: 3px;
cursor: pointer;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="logo">LOGO </div>
<p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p><p> Page content go here<br /> and here<br /> and here<br /> and here<br /> and here</p>
<div id="line"><div id="arrow">V</div></div>
你的方法看起来像是在过度思考它。我正在看HTML progress 元素转为180度视觉。然后，设置它 value 当用户滚动时，用JS动态地归属，并且该线基本上看起来像是动画下来的。
// PROGRESS INDICATOR
// Calculate height of main object and the window, set max attr of progress accordingly
var winHeight = $(window).height(),
sectionHeight = $('#line').height(),
progressBar = $('progress'),
max,
value;
// Set the maximum scrollable area
max = sectionHeight - winHeight;
progressBar.attr('max', sectionHeight);
// Set value attr of progress, changes as user scrolls
$(document).on('scroll', function(){
value = $(window).scrollTop();
progressBar.attr('value', value);
});
progress元素的CSS看起来像这样，你将栏放在页面上作为一个固定元素，并动画它以逐步覆盖上面JS的页面。
CSS示例：
progress {
appearance: none;
-webkit-appearance: none;
-moz-appearance: none;
background-color: transparent;
border: none; //firefox fix
color: green;
height: 2.5rem;
margin-top: 20vw;
position: fixed;
top: 8rem;
width: 100vh;
@media (min-width: 768px) and (max-width: 1200px) {
display: block;
transform: rotate(90deg) translateY(1800%);
}
@media (min-width: 1200px) {
display: block;
transform: rotate(90deg) translateY(1200%); // matches content shift to smaller column
}
}
我建造了 这在我的一个客户端网站上 如果你想看看是否在野外工作（只能在大约1000px和更高的工作，所以要确保你的窗口足够宽）。