Imitation Taobao scrolling sidebar
Case situation:
- Originally sidebar is absolute positioning
- When the page scroll to a certain position, the sidebar changed to a fixed positioning
- Page continues to roll, will be displayed Back to top
case study:
- Need to use the page scroll scroll event because it is the page scrolling, the event is a source document
- Scroll to a position, the upper value of the page is determined to be the volume.
- Page rolled to head: If you can get is to the left window.pageXOffset volumes by window.pageYOffset
- Note that the element is rolled to the head is element.scrollTop, if the page is rolled to the head is window.pageYOffset
- This value can be obtained by offsetTop box, if this value is greater than or equal, so that the box can be positioned in a fixed
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<Title> imitation Taobao sidebar </ title>
<style>
* {
margin: 0;
padding: 0;
}
.slider_box {
position: absolute;
left: 50%;
margin-left: 550px;
top: 456px;
z-index: 3;
/* margin-left: 600px; */
}
.slider_box li {
width: 50px;
height: 50px;
list-style: none;
background-color: pink;
border: 1px solid #ccc;
text-align: center;
line-height: 50px;
font-size: 12px;
}
.container {
position: relative;
width: 1200px;
}
.slider_box .backward {
display: none;
}
.title {
width: 1200px;
height: 100px;
background-color: pink;
}
.header {
width: 1200px;
height: 300px;
background-color: chocolate;
}
.banner {
margin-top: 10px;
width: 1200px;
height: 500px;
background-color: blue;
}
.main {
margin-top: 10px;
width: 1200px;
height: 800px;
background-color: chartreuse;
}
</style>
</head>
<body>
<div class="slider_box">
<ul>
<li></li>
<Li class = "backward"> Top </ li>
<li></li>
<li></li>
</ul>
</div>
<div class="container">
<div class="title"></div>
<div class="header">header</div>
<div class="banner">banner</div>
<div class="main">main</div>
</div>
<script>
1 // Get element
var slider_box = document.querySelector('.slider_box');
var banner = document.querySelector('.banner');
var main = document.querySelector('.main');
var backward = document.querySelector('.backward')
// banner.offestTop is the size of the volume to the head must be written scroll out
was bannerh = banner.offsetTop;
was sliderh = slider_box.offsetTop;
was bhight = sliderh - bannerh;
var mainh = main.offsetTop;
// 2. Scroll event page scroll
document.addEventListener('scroll', function() {
// 3. When are we page volume greater than or equal to the height of the head banner and sidebar will changed to a fixed positioning
if (window.pageYOffset >= bannerh) {
slider_box.style.position = 'fixed';
slider_box.style.top = bhight + 'px';
} else {
slider_box.style.position = 'absolute';
slider_box.style.top = sliderh + 'px';
}
// 4. When we scroll the page to the main box is displayed backward module
if (window.pageYOffset >= mainh) {
backward.style.display = 'block';
} else {
backward.style.display = 'none';
}
})
</script>
</body>
</html>