Vue.component('child-component', {
    template: '<div>Child</div>',
  mounted() {
    this.$emit('test');
  },
  methods: {
    onClick: function() {
        this.$emit('child-click-on');
    }
  }
 });

var vm = new Vue({
    el: '#app',
    created: function () {
        this.$on('test', function () {
            console.log('test-on');
        });
        this.$on('child-click', function () {
            console.log('child-click-on');
        });
    }
});