可以用CSS3做一个动画效果
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>CSS3 过渡效果</title>
<style>
div {
width: 200px;
height: 100px;
background-color: pink;
/* transition: 变化的属性 花费时间 运动曲线 何时开始; */
/* transition: width .5s ease 0s, height .5s ease 1s; */
/* 如果想要写多个属性，利用逗号进行分割 */
/* transition: width .5s, height .5s; */
/* 如果想要多个属性都变化，属性写all就可以了 */
/* transition: height .5s ease 1s; */
/* 谁做过渡，给谁加 */
transition: all 0.5s;
}
div:hover {
width: 400px;
height: 200px;
background-color: skyblue;
}
</style>
</head>
<body>
<div></div>
</body>
</html>
以下为案例学习：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>CSS3过渡练习-进度条</title>
<style>
.bar {
width: 150px;
height: 15px;
border: 1px solid red;
border-radius: 7px;
padding: 1px;
}
.bar_in {
width: 50%;
height: 100%;
background-color: red;
/* 谁做过渡给谁加 */
transition: all .7s;
}
.bar:hover .bar_in {
width: 100%;
}
</style>
</head>
<body>
<div class="bar">
<div class="bar_in"></div>
</div>
</body>
</html>
