python/Day21-30/code/new/web1901/js_practice_4.html

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2024-12-04 00:04:56 +08:00
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>轮播广告</title>
<style>
#adv {
width: 600px;
margin: 0 auto;
}
</style>
</head>
<body>
<div id="adv">
<img src="images/slide-1.jpg" width="600" alt="">
</div id="adv">
<script>
// document.getElementById('标识') ---> HTMLElement [!]
// document.getElementsByTagName('标签名') ---> NodeList
// document.getElementsByClassName('类名') ---> NodeList
// document.querySelector('样式表选择器') ---> HTMLElement [!]
// document.querySelectorAll('样式表选择器') ---> NodeList [!]
// firstChild / lastChild / children --- 获取子节点
// parentNode --- 获取父节点
// previousSibling / nextSibling --- 获取兄弟
const img = document.querySelector('#adv>img')
const imageNames = ['slide-1', 'slide-2', 'slide-3', 'slide-4']
var imageIndex = 0
function switchImage() {
imageIndex += 1
imageIndex %= imageNames.length
img.src = 'images/' + imageNames[imageIndex] + '.jpg'
}
var timerId = setInterval(switchImage, 2000)
img.addEventListener('mouseover', () => clearInterval(timerId))
img.addEventListener('mouseout', () => {
timerId = setInterval(switchImage, 2000)
})
</script>
</body>
</html>