{{input type="number"}}

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  actions: {
  	numberChanged(e) {
      const stringValue = e.currentTarget.value;
      const numValue = parseFloat(stringValue);
      console.log("No, really, this is a number!", numValue, typeof numValue);
      this.set('data', numValue);
    }
  }
});

controllers.application.js

import Ember from 'ember';
import { computed } from '@ember/object';


export default Ember.Controller.extend({
  appName: '{{input type="number"}}',
  myNumber: 3,
  typeOfMyNumber: computed('myNumber', function() {
  	return typeof this.myNumber;
  })
});

templates.application.hbs

<h1>{{appName}}</h1>
<br>

myNumber: {{my-component data=myNumber}}
is a {{typeOfMyNumber}}

{{outlet}}

<footer>
  <p>
    <strong>Instructions:</strong>
    Click the up/down spinner or enter new values for <code>myNumber</code> and observe its type.
  </p>
  <p>
    <strong>Problem/Question:</strong>
    Why isn't <code>myNumber</code> always a number?
  </p>
  
  
  <hr>
  {{!-- 
  
!!! SPOILER ALERT !!! 
Answers / hints may be below here, so don't scroll down unless you want to see them.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
... just a little further ...





  
  
  
  
  
  
  
  --}}
  <style>
    ul {
      list-style: none;
    }
    summary + p {
      margin-left: 18px;
    }
    summary {
      margin-bottom: 8px;
    }
  </style>
  <details>
    <summary>Hints</summary>
    <ul>
    	<li>
        <details>
          <summary>Hint #1</summary>
          <p>
            What happens after the <code>change</code> action fires?
          </p>
        </details>
      </li>
    	<li>
        <details>
          <summary>Hint #2</summary>
          <p>
          Would the same problem happen if we used <code>&lt;input ...&gt;</code> instead of <code>&#123;{input ...}}</code>?
          </p>
        </details>
      </li>
    </ul>
  </details>
  <details>
    <summary>Answer</summary>
    :P
  </details>
  <p>
    Check out more puzzlers at
    <a href="https://github.com/EmberMN/ember-puzzlers/">EmberMN/ember-puzzlers</a>.
  </p>
</footer>

templates.components.my-component.hbs

{{input
  type="number"
  value=data
  change=(action "numberChanged")
}}

twiddle.json

{
  "version": "0.15.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.4.3",
    "ember-template-compiler": "3.4.3",
    "ember-testing": "3.4.3"
  },
  "addons": {
    "ember-data": "3.4.2"
  }
}