https://stackoverflow.com/questions/44731740/ember-object-that-does-not-implement-ember-copyable

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  item: Ember.Object.create({
    name:' SampleName',
    date: Date(),
    amount: 15,    
  }),
  actions:{
    addItem(){
      let temp = this.get('item');
      console.log(' temp ', temp);
      this.set('model',this.store.createRecord('expense', JSON.parse(JSON.stringify(this.get('item')))));
    }
  }
});

models.expense.js

import Model from "ember-data/model";
import attr from "ember-data/attr";
import { belongsTo, hasMany } from "ember-data/relationships";

export default Model.extend({
  name: attr('string',{ defaultValue: 'Sample Name'}),
  date: attr('date',{
    defaultValue(){
      //You can write some code and the return the result.            
      return Date();
    }
  }),
  amount: attr('number',{ defaultValue: 10}),
  totalAmount: Ember.computed('amount',function(){
    return this.get('amount')*10;
  })	
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  model(){
    return this.store.createRecord('expense');
  }
});

templates.application.hbs

<h1 {{action 'addItem'}}>Welcome to {{appName}}</h1>
<br>
{{model.name}}
{{model.date}}
{{model.amount}}
{{model.totalAmount}}
<br>
{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.12.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.12.0",
    "ember-template-compiler": "2.12.0",
    "ember-testing": "2.12.0"
  },
  "addons": {
    "ember-data": "2.12.1"
  }
}