Javascript in Drupal

I was following this post on drupal.org – https://www.drupal.org/node/3075055

But I’m not getting the same result. I’m not experienced at all in javascript so maybe I’m missing something. Do I need to indicate where is my js file? The name of the js file is important?

My module code below:

function draws_form_alter(&$form, &$form_state, $form_id) {
  switch($form_id) {
    case 'bets_node_form':
      $form['field_possible_returns']['und'][0]['value']['#process'] = array('my_custom_process');
      break;
  }
}

function my_custom_process($element, &$form_state, $complete_form){
  $element['field_possible_returns'] = array(
    '#type' => 'textfield',
    '#size' => 8,
    '#attributes' => array(
      'readonly' => 'readonly',
      'tabindex' => -1,
    ),
  );
  return $element;
}

The name of my module is draws.

My javascript file (in the same folder of the module file):

(function ($) {
  Drupal.behaviors.draws = {
    attach: function (context, settings) { 
      alert('Its working!');
      $('.field-name-field-bet-value').on('keyup change', function (){
        var bet_value = $('.field-name-field-bet-value input').val();
        var odd = $('.field-name-field-odd input').val();
        var result = (odd * bet_value).toFixed(2);

        $('.field-name-field-possible-returns input').val(result);
      });
    }
  };
}(jQuery));

Here are the field names of my content type bets:

Thank you.

function draws_form_alter(&$form, &$form_state, $form_id) {
  switch($form_id) {
    case 'bets_node_form':
      $form['field_possible_returns']['und'][0]['value']['#process'] = array('my_custom_process');
      // Load JS File
      $form['#attached']['js'] = [
         drupal_get_path('module', 'draws') . '/draws.js',
      ];
      break;
  }
}