下面是JavaScript滚轮控制模拟滚动条的完整攻略。
1. 目标
我们的目标是实现一个通过鼠标滚轮来控制网页中自定义滚动条的滚动的效果。具体需求包括：
- 鼠标滚动时，滚动条向上或向下滚动一定距离。
- 滚动条的位置要动态显示，并且可以通过拖动来控制滚动条位置。
- 滚轮滚动距离与滚动条滚动距离的比例要保持一致。
- 滚动条需要自适应网页高度变化。
2. 分析
为了实现目标，我们需要了解到以下内容：
- 滚轮事件的绑定
- 滑动条的拖动事件绑定
- 滑动条的位置变化
- 网页高度变化时滑动条的变化
针对以上要求，我们可以采用如下方案：
-
监听滚轮事件，获取滚轮滚动的方向，然后计算出滚动量，从而改变页面滚动的位置，并且更新滑动条的位置。
-
监听滑动条的拖动事件，获取滑动条的拖动位置，从而改变页面滚动的位置，并且更新滑动条的位置。
-
监听窗口的resize事件，从而自适应网页高度变化，并更新滑动条的位置。
3. 实现
以下是一个基本实现，我们使用了HTML、CSS和JavaScript：
<!DOCTYPE html>
<html>
<head>
<title>JavaScript滚轮控制模拟滚动条</title>
<style>
#content {
width: 400px;
height: 300px;
overflow: hidden;
position: relative;
}
#scrollbar {
width: 4px;
height: 100%;
position: absolute;
top: 0;
right: 0;
background: #ccc;
border-radius: 2px;
z-index: 99;
opacity: 0.5;
transition: all 0.2s ease;
}
#scrollbar:hover {
opacity: 1;
}
</style>
</head>
<body>
<div id="content">
<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nam sit amet lorem ac ante gravida sodales. Sed ut dui est. Suspendisse potenti. Ut laoreet dui massa, id convallis augue viverra quis. Aliquam rutrum justo et nisl varius, sed ullamcorper libero fringilla. Nam vel ex id lorem bibendum maximus in eget ex. Curabitur vel justo ex. Aliquam ultricies, nunc vitae suscipit semper, ipsum dolor aliquet neque, at vehicula diam diam vitae nibh.</p>
<p>Integer vestibulum mollis leo ut aliquet. Praesent fermentum, arcu eu venenatis semper, tellus ipsum elementum leo, id sagittis nunc ante eget ligula. Cras sed metus et libero auctor convallis non vel ante. Etiam quis velit diam. In a odio a dui feugiat porta. Sed ac felis vel velit feugiat pharetra vitae vitae ex. Vivamus mollis neque dolor, eget vehicula enim bibendum ut. Praesent vehicula, nisi at lobortis luctus, lacus dui posuere mi, id ornare mi massa vel est. Quisque ornare mi sit amet placerat bibendum. Ut a lobortis ex. Nullam sagittis mauris quis porta tincidunt.</p>
<p>Morbi bibendum eros enim, vitae eleifend enim dictum ac. Donec fringilla odio vel justo ornare, id ornare sapien efficitur. Phasellus bibendum malesuada tellus vel blandit. Vivamus imperdiet ante ipsum, vitae iaculis est tempus quis. Sed auctor, nisi vel luctus ullamcorper, velit dolor ornare sapien, vel mattis nibh enim auctor magna. Nullam eleifend nibh ullamcorper vehicula dignissim. Sed leo eros, semper a enim eu, efficitur cursus justo. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia curae; Praesent lacinia mollis justo, nec iaculis ante ullamcorper sed.</p>
<p>Aenean odio diam, venenatis at enim ut, euismod vehicula felis. In bibendum, sapien quis dapibus varius, velit lacus imperdiet eros, ac iaculis nibh lectus sed ipsum. Sed eget gravida sapien. Morbi mattis lacus at elit consectetur tincidunt. Sed consectetur, ipsum id aliquet maximus, velit nisi laoreet odio, eget tempus enim magna in sapien. Integer lobortis mi ut dapibus sagittis. Fusce ornare pulvinar libero non pellentesque. Aenean non urna nulla. Etiam condimentum laoreet enim, eget bibendum magna hendrerit nec. Aliquam non nisl vel massa consequat dignissim.</p>
<p>Etiam faucibus, nulla vel porttitor tincidunt, leo dolor faucibus justo, in dapibus dui neque a mauris. Morbi finibus dolor quis turpis tempor, vel egestas arcu luctus. Vestibulum eu quam a arcu fermentum viverra. Sed nec libero semper, porta velit nec, tincidunt erat. Nulla facilisi. Integer tincidunt tincidunt hendrerit. Nunc suscipit felis augue, sit amet convallis urna vulputate vel. Sed sagittis vehicula lorem sed auctor. Integer volutpat mauris justo, quis varius mauris fermentum eu. Suspendisse rutrum laoreet mi, non venenatis ex molestie eu.</p>
<p>Vivamus auctor magna id nulla auctor volutpat. Quisque euismod finibus eros, ut tincidunt erat mollis ut. Vivamus rhoncus pellentesque nisi, non sagittis sem consequat vel. Ut consectetur ornare ornare. Fusce ornare erat ut diam convallis tincidunt. Nulla quis dolor posuere, malesuada leo ut, mollis urna. Suspendisse facilisis ipsum bibendum, auctor dolor ut, commodo lacus. Aliquam a porta diam. Fusce luctus ligula ac semper porta.</p>
</div>
<div id="scrollbar"></div>
<script>
var content = document.getElementById('content');
var scrollbar = document.getElementById('scrollbar');
var contentHeight = content.clientHeight;
var containerHeight = content.parentNode.clientHeight;
var scrollRatio = containerHeight / contentHeight;
var thumbHeight = containerHeight * scrollRatio;
scrollbar.style.height = thumbHeight + 'px';
function scrollContent(delta) {
var initial = content.scrollTop;
var step = 10 * delta;
content.scrollTop += step;
var final = content.scrollTop;
var thumb = scrollbar.offsetHeight;
var move = thumb * (final - initial) / (contentHeight - containerHeight);
var pos = parseInt(scrollbar.style.top) || 0;
scrollbar.style.top = (pos + move) + 'px';
}
function dragThumb(evt) {
evt.preventDefault();
var startY = evt.clientY;
var startTop = parseInt(scrollbar.style.top) || 0;
var doDrag = function(evt) {
var moveY = evt.clientY - startY;
var endTop = Math.min(Math.max(startTop + moveY, 0), containerHeight - thumbHeight);
scrollbar.style.top = endTop + 'px';
var scrollTop = (contentHeight - containerHeight) * endTop / (containerHeight - thumbHeight);
content.scrollTop = scrollTop;
}
var stopDrag = function(evt) {
document.removeEventListener('mousemove', doDrag);
document.removeEventListener('mouseup', stopDrag);
}
document.addEventListener('mousemove', doDrag);
document.addEventListener('mouseup', stopDrag);
}
function updateThumb() {
contentHeight = content.clientHeight;
containerHeight = content.parentNode.clientHeight;
scrollRatio = containerHeight / contentHeight;
thumbHeight = containerHeight * scrollRatio;
scrollbar.style.height = thumbHeight + 'px';
var pos = parseInt(scrollbar.style.top) || 0;
scrollbar.style.top = Math.min(pos, containerHeight - thumbHeight) + 'px';
}
scrollbar.addEventListener('mousedown', dragThumb);
content.addEventListener('wheel', function(evt) {
evt.preventDefault();
var delta = Math.max(-1, Math.min(1, evt.deltaY));
scrollContent(delta);
});
window.addEventListener('resize', updateThumb);
</script>
</body>
该代码实现了一个模拟滚动条的效果，在滚动时会通过拖动滑块或滚动鼠标滚轮来滚动页面，并同步显示滑块位置。
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