New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle', 
  arr1: [{date: Date.now()}],
  arr2: [{date: Date.now()}],
  arr3: [{date: Date.now()}],
  array1Contents: Ember.computed('arr1.length', function() {
  	return this.get('arr1').map(i => i.date).join(',');
	}),
  array2Contents: Ember.computed('arr2', function() {
  	return this.get('arr2').map(i => i.date).join(',');
  }),
 array3Contents: Ember.computed('[email protected]', function() {
  	return this.get('arr3').map(i => i.date).join(',');
	}),
  
  actions: {
  	replaceArray(name) {
      this.set(name, [{date: Date.now()}]);
    },
    pushArray(name){
   	 this.get(name).pushObject({date: Date.now()});
    },
    replaceItem(name) {
    	this.set(`${name}.0.date`, Date.now());
    }
  }
});

templates.application.hbs

<b>overwrite array</b> - sets new array under property <br>
<b>pushArray</b> - addes new element to array <br>
<b>replace Item in Array</b> - calls set on first element of array
<br>
<br>
arr2: {{array2Contents}} - that works only if whole array was overwriten <br>
<button {{action "replaceArray" 'arr2'}}>overwrite array</button>
<button {{action "pushArray" 'arr2'}}>pushArray</button>
<button {{action "replaceItem" 'arr2'}}>replace Item in Array</button>
<br/> <br/> 
arr1: {{array1Contents}} - that works if array length has changed <br/>

<button {{action "replaceArray" 'arr1'}}>overwrite array</button>
<button {{action "pushArray" 'arr1'}}>pushArray</button>
<button {{action "replaceItem" 'arr1'}}>replace Item in Array</button>

<br/> <br/> 
arr3: {{array3Contents}} - that works if any item in array has changed <br>
<br/>
<button {{action "replaceArray" 'arr3'}}>overwrite array</button>
<button {{action "pushArray" 'arr3'}}>pushArray</button>
<button {{action "replaceItem" 'arr3'}}>replace Item in Array</button>

{{outlet}}
<br>
<br>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0"
  }
}