Group by first character

controllers.application.js

import Ember from 'ember';
import groupBy from 'ember-awesome-macros/array/group-by';
import raw from 'ember-macro-helpers/raw';

export default Ember.Controller.extend({
  categories: [
    { name: 'Hello' },
    { name: 'Hallo' },
    { name: 'World' },
    { name: 'Welt' }
  ],
  
  grouped: groupBy('categories', raw('name.0'))
});

templates.application.hbs

<ul>
  {{#each grouped as |group|}}
    <li>
      <strong>{{group.value}}</strong>
      <ul>
        {{#each group.items as |item|}}
          <li>{{item.name}}</li>
        {{/each}}
      </ul>
    </li>
  {{/each}}
</ul>

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-awesome-macros": "3.0.0"
  }
}