New Twiddle

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
    percentage: 0.21,

    actions: {
        increment(value) {
            this.incrementProperty('percentage', value);
        },
        decrement(value) {
            this.decrementProperty('percentage', value);
        }
    }
});

styles.app.css

body {
  margin: 12px 16px;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 12pt;
}

input[type="number"] {
  width: 200px;
}

templates.application.hbs

<h1>Wrong floating point</h1>

<p>When incrementing or decrementing an floating point by .01, it often returns the wrong value. Also when the floating point is updated by one (not a decimal) it can sometimes do the same.<br>
For example: 0.03 + 0.01 = 0,0400000000000001</p>
<br /><br />

{{input type="number" value=percentage}} %

<br /><br />

<button {{action "increment" 0.01}}>Decrement (- 0.01)</button>

<button {{action "decrement" 0.01}}>Increment (+ 0.01)</button>

<br /><br />

<button {{action "increment" 1}}>Decrement (- 1)</button>

<button {{action "decrement" 1}}>Increment (+ 1)</button>

twiddle.json

{
  "version": "0.7.0",
  "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"
  }
}