我自定义了watch对象如下

app.vue
<template>
  <div id="app">
    <img src="./assets/logo.png">
    <h4 v-if="show">{{msg}}</h4>
    <h4 v-else>{{msg2}}</h4>
    <h6 v-if="infoShow">msg changed</h6>
    <a @click="toggle" class="btn-toggle" style="color: red; border: 1px solid black">toggle</a>
    <a @click="changeMsg" style="color: green">change</a>
  </div>
</template>

<script>
import Vue from 'vue'

export default {
  name: 'App',
  data(){
    return {
      msg: "screen one when show is true",
      msg2: "screen two",
      show: true,
      infoShow: false
    }
  },
  methods: {
    toggle() {
      this.show = !this.show;
    },
    changeMsg() {
      debugger;
      this.msg = "screen one when show is true " + Math.random();
    }
  },
  watch:{
    msg(nValue, oValue){
      
      this.infoShow = true;  
    }
  }
}
</script>

在自定义watcher初始化中遇到了下面的代码

请问这个正则匹配怎样的字符串

^a-zA-Z\u00B7\u00C0-\u00D6\u00D8-\u00F6\u00F8-\u037D\u037F-\u1FFF\u200C-\u200D\u203F-\u2040\u2070-\u218F\u2C00-\u2FEF\u3001-\uD7FF\uF900-\uFDCF\uFDF0-\uFFFD.$_\d

我通过正则可视化工具发现

怎么字符串结尾还要匹配规则 ,怎样的字符串符合要求呢 谢谢！