Edit in JSFiddle

  const vm = new Vue({
    el: "#app",
    data: {good: 0, bad: 0},
    created: function() {
      this.$once("foo", function(e) { this[e.target.dataset.key] += 1 })
    },
    methods: {
      a: function(e) { this.$emit("foo", e) },
    },
  })
<div id="app">
  <div class="btn btn-link glyphicon glyphicon-hand-up" @click="a" data-key="good">
    {{good}}
  </div>
  <div class="btn btn-link glyphicon glyphicon-hand-down" @click="a" data-key="bad">
    {{bad}}
  </div>
</div>