<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>事件处理</title>
</head>
<body>
    <div id="app">
        <button v-on:click="changeLength($event)" value="1">边长加1</button>
        <button v-on:click="changeLength($event)" value="10">边长加10</button>
        <p>正方形的边长是{{length}}，面积是{{area}}</p>
    </div>

    <script src="../js/vue.js"></script>

    <script>
        let square = {
            length:2
        };

        let vm = new Vue({
            el:'#app',
            data:square,
            methods:{
                changeLength(event) {
                    this.length += Number(event.target.value);
                }
            },
            computed:{
                area(){
                    return this.length * this.length;
                }
            }
        });
    </script>
</body>
</html>