VUE中的无限循环代码解析

<template>
<div id="">
 <ul v-for="(item,index) in listaaa">
  <li v-if='dealFun(item.cdate,index)'>{{item.cdate}}</li>
 </ul>
</div>
</template>
<script>
export default {
 name: "",
 data(){
   return {
     listaaa: [{
       cdate: '123'
      },
      {
       cdate: '456'
      },
     ],
     flagName: ''
   }
 },
 methods: {
  dealFun(arg, index) {
   console.log('---------------------------')
   if (arg == this.flagName) {
    return false
   } else {
    this.flagName = arg
    return true
   }
  }
 },
}
</script>
<style scoped>
</style>

<template>
<div id="">
 <ul v-for="(item,index) in listaaa">
  <li v-if='dealFun(item.cdate,index)'>{{item.cdate}}</li>
 </ul>
</div>
</template>
<script>
var flagName;
export default {
 name: "",
 data(){
   return {
     listaaa: [{
       cdate: '123'
      },
      {
       cdate: '456'
      },
     ],
    //  flagName: ''
   }
 },
 methods: {
  dealFun(arg, index) {
   console.log('---------------------------')
   if (arg == flagName) {
    return false
   } else {
    flagName = arg
    return true
   }
  }
 },
}
</script>
<style scoped>
</style>