基础
html
<!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
html
<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>