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css3

news 2025/7/28 2:33:47

基础

<!DOCTYPE html>
<html><head><meta charset="utf-8"><title>style</title><!-- link（外部样式）和style（内部样式）优先级相同，重复写会覆盖 --><link rel="stylesheet" href="main.css"/><style>/* 标签选择器 */h1 {background-color: aquamarine;/* !important 表示优先级最高 */color: black !important;}/* 类选择器 */.class1{color: red;}/* id选择器 */#id1{color: blue;}/* 后代选择器：#id2内所有的p标签 */#id2 p{color: royalblue;}/* 子代选择器：#id2的第一级子标签 */#id2 > p{text-decoration-line: underline;}/* 伪类选择器：需要有a的选择器 */a{}/* 鼠标置于a标签，颜色改变 */a:hover {color: red;}a:link{color: yellow;}a:visited{color: green;}a:active{color: blue;}body{background-color: aliceblue;background-image: url("../img/demo2.png");background-repeat: no-repeat;background-size: 200px 200px;/* 背景固定 */background-attachment: fixed;/* 背景随滚动条滚动 *//* background-attachment: scroll; */background-position-x: center;background-position-y: center;/* xy轴占比 */background-position: 10% 10%;}span{/* font-size: 20px;font-family: "Microsoft YaHei UI";font-weight: bold;font-style: italic; *//* 连写要注意顺序 */font: italic bold 30px "Microsoft YaHei UI";}p{font-size: 16px;width: 120px;color: crimson;line-height: 24px;/* 缩进 */text-indent: 1em;}</style></head><body><!-- 行内样式优先级高于内部样式 --><h1 style="background-color: aqua; text-align: center;">111</h1><h1 class="class1">222</h1><h1 id="id1">333</h1><div id="id2"><p>p1</p><div><p>p2</p></div></div><a href="">百度</a></body>
</html>

计时器

<h1 id="clock"></h1>
<script>const formatTime = n => n < 10 ? '0' + n : n;function updateClock(){const date = new Date();const hours = formatTime(date.getHours());const minutes = formatTime(date.getMinutes());const seconds = formatTime(date.getSeconds());const clock = document.getElementById("clock");clock.textContent = `${hours}:${minutes}:${seconds}`;}setInterval(updateClock,1000);
</script>