pa

controllers.application\.js

import Controller from '@ember/controller';
import { TrackedArray } from 'tracked-built-ins';
import { action } from '@ember/object';

export default class ApplicationController extends Controller {
  appName = 'particial application';
  values = new TrackedArray([0, 1, 2, 3, 4, 'omg']);

  @action handleInput(event) {
    this.values[0] = event.target.value;
    console.log(this.values)
  }

  @action crappyHandleInput(index) {
    console.log('first call')
    
    this.values[index] = event.target.value;
    console.log('second call');
    console.log(this.values)
  }

  
}
 

styles.app\.css

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

.container {
  display: flex;
  flex-direction: column;
  width: 50%;
  height: 300px;
  justify-content: space-around;

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<div class="container">
<label>
  working input: {{get this.values 0}}
  <input value={{get this.values 0}} {{on "input" this.handleInput}} />
</label>
{{#each this.values key="@index" as |value index|}}
  {{#if index}}
  <label>
  crappy input {{index}}: {{value}}
  <input value={{value}} {{on "input" (fn this.crappyHandleInput index)}} />
  </label>
  {{/if}}
{{/each}}
</div>

twiddle\.json

{
  "version": "0.17.1",
  "EmberENV": {
    "FEATURES": {},
    "_TEMPLATE_ONLY_GLIMMER_COMPONENTS": false,
    "_APPLICATION_TEMPLATE_WRAPPER": true,
    "_JQUERY_INTEGRATION": true
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.1/jquery.js",
    "ember": "3.18.1",
    "ember-template-compiler": "3.18.1",
    "ember-testing": "3.18.1"
  },
  "addons": {
    "@glimmer/component": "1.0.0",
    "tracked-built-ins": "1.1.1"
  }
}