AI 编程工具xxxxxxxxxx<html><head><meta charset="utf-8"><title>Vue 测试实例 - 高手教程(study.p2hp.com)</title><script src="https://lf26-cdn-tos.bytecdntp.com/cdn/expire-1-M/vue/2.6.14/vue.min.js"></script></head><body><div id = "app"> <p style = "font-size:25px;">计数器: {{ counter }}</p> <button @click = "counter++" style = "font-size:25px;">点我</button></div><script type = "text/javascript"> var vm = new Vue({ el: '#app', data: { counter: 1 } }); vm.$watch('counter', function(nval, oval) { alert('计数器值的变化 :' + oval + ' 变为 ' + nval + '!'); });</script></body></html>