<h5>15.侦听器</h5>
<div class="watchs">
	<p>count:{{nowtime}}</p>
	<button @click='nowtime++'>点我</button>
</div>
<pre>注意：tt.$watch('nowtime',function(n,o){/*n为新值，o为旧值*/})</pre>
<script type="text/javascript">
	//监听器
	const timer = Vue.createApp({
		data(){
return{
	nowtime:0
}
		} 
	})
	const tt = timer.mount('.watchs');
	tt.$watch('nowtime',function(n,o){
		alert("此时"+o+'变成了'+n);
	})
</script>

交互效果见：https://course.51qux.com/vue3-0-1