简单vue代码如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<div id="app">
<ul>
<li>西游记; 价格：{{xyjPrice}},数量：<input type="number" v-model="xyjNum"></li>
<li>西游记; 价格：{{shzPrice}},数量：<input type="number" v-model="shzNum"></li>
<li>总价：{{totalPrice}}</li>
<li>{{msg}}</li>
</ul>
</div>
<script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
<script>
new Vue({
el:"#app",
data:{
xyjPrice:99.98,
shzPrice:98.00,
xyjNum: 1,
shzNum:1,
msg:""
},
computed:{
totalPrice(){
return this.xyjPrice*this.xyjNum + this.shzPrice*this.shzNum;
}
},
watch:{
xyjNum:function(newVal,oldVal){
if(newVal>3){
this.msg="库存超出限制！";
}else{
this.msg="";
}
}
}
})
</script>
</body>
</html>
