Each loop interpter

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle'
});

helpers.my-helper.js

import Ember from 'ember';
export function myHelper([index,position,totalLength]) {
  if(index === totalLength-1){
    return '';
  }
  index = index+1;
  return index%position === 0 ? " -- ":"";
}
export default Ember.Helper.helper(myHelper);

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  model(){
  	return [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16];
  }
});

templates.application.hbs

<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>

<h1>Each with condition </h1>
{{#each model as |num index |}}
	{{index}}{{my-helper index 4 model.length}}
 {{/each}}

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"
  }
}