初识Vue 3.0 —— $watch:侦听器

<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​​

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