精彩的助手！
我正在尝试创建一个时间轴元素，根据滚动位置为#marker上的CSS width属性设置动画。我是jQuery的新手，我知道我可能有一些错误...抱歉。从好的方面来说，我确实提出了有用的评论来解释我正在尝试做什么。请看一下，并提前致谢！
<!DOCTYPE html>
<head>
<!-- CSS Styles Link -->
<link rel='stylesheet' type='text/css' href='styles.css'>
<!-- jQuery Library Link -->
<script type='text/javascript' src='jquery-awesomeness.js'></script>
<script>
var marker = $('#marker') // Converts CSS #marker into a jQuery variable named $marker
var height = $(window).scrollTop(); // Uses jQuery scrollTop method to detect scroll position and sets it as a variable named height
// Jquery for Timeline
$(document).ready(function(){ //Prevents jQuery from performing instructions until after the page has loaded
if(height > height + 100 ) { // Creates a conditional statement - if the scroll position increases by 100, do the following instructions
marker.css('width', +10% // Increase CSS width setting on #marker by 10%.
}); // Closes first conditional statement
else if (height < height + 100 ) { // Creates another conditional statement - if the scroll position increases by 100, do the following instructions
marker.css('width', -10% // Decrease CSS width setting on #marker by 10%
}); // Closes second conditional statement
}); // Closes document dot ready function
</script>
</head>
<body>
<!-- HTML Code for Timeline elements -->
<div id='timeline'> <!-- Timeline's main container -->
<div id='path'></div><!-- Timeline's inner path -->
<div id='marker'></div><!-- Timeline's animatable marker -->
</div>
<div id='content1'>
<p>
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum dolor turpis, consectetur vel libero a, mollis dapibus odio. Nunc lobortis, eros non tincidunt porttitor, purus tellus porta lectus, non luctus arcu augue eu est. Nunc malesuada ex elit, vel bibendum erat dictum nec. Proin imperdiet efficitur elit eu vestibulum. Nullam id augue tincidunt, efficitur nunc non, efficitur urna. Proin sit amet tincidunt purus. Sed interdum, felis quis facilisis malesuada, felis felis viverra lectus, eget euismod elit risus et mi. Mauris eu enim tellus. Aenean tincidunt orci nec tincidunt facilisis. Phasellus dignissim ante ut maximus feugiat. Mauris sollicitudin venenatis neque nec luctus. Quisque vel tempus urna, sed feugiat leo. Sed tellus magna, molestie non purus in, viverra condimentum orci. Nulla a nunc mauris. Aliquam convallis interdum velit, ac luctus massa rutrum at.
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</p>
</div>
</body>
</html>
CSS：
#timeline {
width: 98%;
height: 1%;
margin: 1%;
padding-top: 1%;
padding-bottom: 1%;
position: fixed;
bottom: 0;
left: 0;
background-color: #590C13;
border-radius: .5em;
}
#path {
width: 98%;
position: fixed;
border-top: 3px solid #424343;
}
#marker {
width: 0%; /* This is defaulted to zero. jQuery resets value based on scroll position. Don't mess with it! */
position: relative;
top: 0;
border-top: 3px solid #ffffff;
}
p { /* This is place holder content used to test jQuery scroll position. Feel free to delete. */
padding: 3%;
font-size: 2em;
line-height: 3em;
}
答案 0 :(得分：0)
我已经重新设置了CSS，并且还编写了在滚动或调整视口大小时更新标记宽度的逻辑。 CSS主要涉及将#marker和#path更改为绝对定位而不是固定：
#path {
width: 100%;
position: absolute;
border-top: 3px solid #424343;
}
#marker {
width: 0;
absolute;
border-top: 3px solid #ffffff;
}
对于计算，诀窍如下：
现在这里是jQuery中的逻辑。我选择在名为updateMarker()的函数中进行计算，因此我们可以在视口大小更改时或用户滚动时调用它。您还应该将其称为onload（如果用户没有从页面顶部开始）。
$(function() {
var updateMarker = function() {
// Update measurements
var viewportHeight = $(window).height(),
contentHeight = $('#content1').height(),
pathWidth = $('#path').width(),
scrollPosition = $(window).scrollTop();
// Update #marker dimensions
$('#marker').width(scrollPosition/(contentHeight-viewportHeight)*pathWidth);
}
// Call function when viewport is resized or scrolled
$(window).on('scroll resize', updateMarker);
// Call function on DOM ready
updateMarker();
});
请参阅此处的小提琴：http://jsfiddle.net/teddyrised/e0ezfw6w/
ps：在旁注中，您可能需要consider use the <progress> element，这在语义上比<div>更具相关性;）