Nesting helpers

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Nested helpers',
  emberVersion: Ember.VERSION
});

helpers.one.js

import Ember from 'ember';

export function one(params/*, hash*/) {
  return `(1) ${params[0]}`;
}

export default Ember.Helper.helper(one);

helpers.three.js

import Ember from 'ember';

export function three(params/*, hash*/) {
  return `(3) ${params[0]}`;
}

export default Ember.Helper.helper(three);

helpers.two.js

import Ember from 'ember';

export function two(params/*, hash*/) {
  return `(2) ${params[0]}`;
}

export default Ember.Helper.helper(two);

templates.application.hbs

Ember {{emberVersion}}
<h1>{{appName}}</h1>
{{one (one 'a')}}
<br />
{{one (two (three 'b'))}}
<br />
{{outlet}}

twiddle.json

{
  "version": "0.7.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.3/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/2.4.3/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/2.4.3/ember-template-compiler.js"
  }
}