Vue progress input v-model and watch

v-model="xx" => watch:{xx:function(n,o){...} }

<script src="https://unpkg.com/vue"></script>
<div id="bbb">
<input v-model='v'></input>
<progress :value='v2' :max='max' :title='title'></progress>
</div>

new Vue({
 el:'#bbb'
 ,data:{v:10,max:1000,v2:10,title:this.v}
 ,watch:{//v-model:x is watch the x
  v:function(n,o){this.check(n,o)}
 }
 ,methods:{
  check:function(n,o){//new old
   console.log(n,o)
   this.title=n;
   if(isNaN(n))return this.title=`burning value:${n}`
   this.v2=n;
  } 
 }
})