arrays are dumb

controllers.application\.js

import Controller from '@ember/controller';
import {action, computed, set} from '@ember/object';
import {A} from '@ember/array';

export default class ApplicationController extends Controller {
  appName = 'Ember Twiddle';

	numberSelected = 1;

	_nameArray = A(['']);

	@computed('numberSelected', '_nameArray.[]')
  get nameArray() {
    const a = this._nameArray;
    const lengthDifference = Math.abs(this.numberSelected - a.length);
    if (this.numberSelected > a.length) {
      // add name slots
      for (let i = 0; i < lengthDifference; i++) {
        a.push('');
        // a.push({ name: '' });
      }
    } else if (this.numberSelected < a.length) {
      // remove name slots
      const shorterArray = a.slice(0, this.numberSelected);
      return A(shorterArray);
    }

    return A(a);
  }
	set nameArray({value, index}) {
    set(this, `_nameArray.${index}`, value);
  }


	@action
  selected(event) {
    this.set('numberSelected', parseInt(event.target.value));
  }

  @action newValue(index, event) {
    console.log('event', event);
    console.log('index', index);
    this.set('nameArray', {value: event.target.value, index})
  }
}

templates.application\.hbs

<h1>Welcome to {{this.appName}}</h1>
<br>
<br>

<p>{{this.numberSelected}}</p>
<select onchange={{action "selected"}}>
  <option value=1>1</option>
  <option value=2>2</option>
  <option value=3>3</option>
</select>
<br><br><br>

{{#each this.nameArray as |name index|}}
	name: {{name}} <br>
	<input value={{name}} oninput={{action "newValue" index}} />
  <br>
{{/each}}
<br>
<br>

Hidden values <br>
{{#each this._nameArray as |name|}}
	name: {{name}} <br>
  <br>
{{/each}}

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"
  }
}