vue emit

Child.vue

<tmplate lang="pug">
  .child
    .btn(@click="clickBtn")
</tamplate>

<scrpit>
export default {
  ...
  methods: {
    clickBtn: function() {
      this.$emit('clickChild', param);
    }
  }
}
</script>

Parent.vue

<tmplate lang="pug">
  .parent
    .child(@clickChild="onClick")
</tamplate>

<scrpit>
export default {
  ...
  methods: {
    onClick: function(param) {
      console.log(param);
    }
  }
}
</script>