helloworld.vue

<template>
  <div @click="hola">Pulsa aquí</div>
</template>

<script>
import MyMixin from './mixin';
export default {
  name: 'HolaMundo',
  mixins: [MyMixin]
}
</script>

mixin.js

export default {
  data () {
    return {
      
    }
  },
  methods: {
    hola () {
      alert ('hola')
    }
  }
}