New Twiddle

controllers.application.js

import Ember from 'ember';
import { task, timeout, asyncComputed, emit } from 'ember-concurrency';

export default Ember.Controller.extend({
  value: 123,
  
  tweened: asyncComputed('value', function * (v) {
    let targetValue = parseInt(v);
    let curValue = parseInt(this.get('tweened.lastComplete.value') || targetValue);
    while (true) {
      let delta = Math.floor((targetValue - curValue) * 0.6);
      if (delta) {
        curValue += delta;
        yield emit(curValue);
      } else {
        return targetValue;
      }
      yield timeout(50);
    }
  }),
});

templates.application.hbs

<h3>ember-concurrency async computed properties</h3>

<p>{{input value=value type='number'}}</p>

<h1>{{tweened.value}}</h1>

twiddle.json

{
  "version": "0.10.1",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.6.0",
    "ember-data": "2.6.1",
    "ember-template-compiler": "2.6.0"
  },
  "addons": {
    "ember-concurrency": "tof3"
  }
}