selected

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  appName: 'Ember Twiddle',
  actions: {
    testme(something) {
      console.log(something);
      let model = this.get('model');
      for(let i = 0; i < model.length; i++) {
        Ember.set(model[i], 'selected', null);
      }
      let item = model.findBy('department', something);
      console.log(item);
      Ember.set(item, 'selected', true);
      console.log(this.get('model'));
    }
  }
});

routes.application.js

import Ember from 'ember';

export default Ember.Route.extend({
  model() {
		return [
      { 'department': 'intern' },
      { 'department': 'newgrad' },
      { 'department': 'entry' },
      { 'department': 'senior'}
    ];
  }
});

templates.application.hbs

<style>
.colorMe {
background-color: lightblue;
}
</style>
<h1>Welcome to {{appName}}</h1>
<br>
<br>
{{outlet}}
<br>
<br>
<ul>
{{#each model as |test|}}
<li class="{{if test.selected 'colorMe' ''}}" onclick={{action 'testme' test.department}}>{{test.department}} X{{test.selected}}X</li>
{{/each}}
</ul>

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"
  }
}