<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
</head>
<body>
<div id="app">
<!-- <ul class="list">
<li class="item active">1</li>
<li class="item">2</li>
<li class="item">3</li>
</ul> -->
<!-- <ul class="list">
<li class="item" :class="{'active':isActive}">1</li>
<li class="item">2</li>
<li class="item">3</li>
</ul> -->
<ul class="list">
<li class="item" :class="['active']">1</li>
<li class="item" :style="css">2</li>
<li class="item">3</li>
</ul>
</div>
</body>
<script>
var app = new Vue({
el: '#app',
data: {
isActive: true,
css: {color: 'red',}
}
})
</script>
</html>