default.js

import Ember from 'ember';
export default Ember.Route.extend({
    model: function () {
        return {};
    }
    firstName: null,
    lastName: null,

    fullName: Ember.computed('firstName', 'lastName', function() {
        return this.get('firstName') + ' ' + this.get('lastName');
    })
});

full-es6.js

import Ember from 'ember';
export class FullEs6 extends Ember.Route {
    model () {
        return {};
    }
    firstName = null
    lastName = null

    @computed('firstName', 'lastName')
    fullName(firstName, lastName) {
        return `#{firstName} #{lastName}`;
    })
};