<!DOCTYPE html>
<html lang="ch">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>计数器</title>
</head>

<body>
    <div id="app">
        <div class="input_num">
            <button @click="add">+</button>
            <span>{{num}}</span>
            <button @click="sub">-</button>
        </div>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
    <script>
        //创建vue实例
        var app = new Vue({
            el: "#app",
            data: {
                num: 1
            },
            methods: {
                add: function () {
                    if(this.num>=10){
                        alert("别点了,最大10");
                        return;
                    }
                    this.num++;
                },
                sub: function () {
                    if(this.num<=0){
                        alert("别点了,最小0");
                        return;
                    }
                    this.num--;
                }
            }
        })     
    </script>
</body>

</html>