Vue gets the attribute value on the tag

method one: 

<div id="app">
  <button  @click="getData($event,'100')">点我</button>
</div>

methods : {
   getData(e,num) {
        console.log(num);     // 输出 100
   }
}

Method Two:

<div id="app">
  <button data-num="100" ref="dataNum"  @click="getData($event)">点我</button>
</div>

methods : {
   getData (e) {
       console.log(this.$refs.dataNum.dataset.num);     // 输出 100
   }
}

Method three:

<div id="app">
  <button data-num="100" @click="getData($event)">点我</button>
</div>

methods : {
   getData (e) {
       console.log(e.target.getAttribute('data-num'));     // 输出 100
  
   }
}