Woocommerce Checkout Page Input Class Change

add_filter('woocommerce_form_field_args','wc_form_field_args',10,3);

function wc_form_field_args( $args, $key, $value = null ) {

/*********************************************************************************************/
/** This is not meant to be here, but it serves as a reference
/** of what is possible to be changed. /**

$defaults = array(
    'type'              => 'text',
    'label'             => '',
    'description'       => '',
    'placeholder'       => '',
    'maxlength'         => false,
    'required'          => false,
    'id'                => $key,
    'class'             => array(),
    'label_class'       => array(),
    'input_class'       => array(),
    'return'            => false,
    'options'           => array(),
    'custom_attributes' => array(),
    'validate'          => array(),
    'default'           => '',
);
/*********************************************************************************************/

// Start field type switch case

switch ( $args['type'] ) {

    case "select" :  /* Targets all select input type elements, except the country and state select input types */
        $args['class'][] = 'form-group'; // Add a class to the field's html element wrapper - woocommerce input types (fields) are often wrapped within a <p></p> tag  
        $args['input_class'] = array('form-control', 'input-lg'); // Add a class to the form input itself
        //$args['custom_attributes']['data-plugin'] = 'select2';
        $args['label_class'] = array('control-label');
        $args['custom_attributes'] = array( 'data-plugin' => 'select2', 'data-allow-clear' => 'true', 'aria-hidden' => 'true',  ); // Add custom data attributes to the form input itself
    break;

    case 'country' : /* By default WooCommerce will populate a select with the country names - $args defined for this specific input type targets only the country select element */
        $args['class'][] = 'form-group single-country';
        $args['label_class'] = array('control-label');
    break;

    case "state" : /* By default WooCommerce will populate a select with state names - $args defined for this specific input type targets only the country select element */
        $args['class'][] = 'form-group'; // Add class to the field's html element wrapper 
        $args['input_class'] = array('form-control', 'input-lg'); // add class to the form input itself
        //$args['custom_attributes']['data-plugin'] = 'select2';
        $args['label_class'] = array('control-label');
        $args['custom_attributes'] = array( 'data-plugin' => 'select2', 'data-allow-clear' => 'true', 'aria-hidden' => 'true',  );
    break;


    case "password" :
    case "text" :
    case "email" :
    case "tel" :
    case "number" :
        $args['class'][] = 'form-group';
        //$args['input_class'][] = 'form-control input-lg'; // will return an array of classes, the same as bellow
        $args['input_class'] = array('form-control', 'input-lg');
        $args['label_class'] = array('control-label');
    break;

    case 'textarea' :
        $args['input_class'] = array('form-control', 'input-lg');
        $args['label_class'] = array('control-label');
    break;

    case 'checkbox' :  
    break;

    case 'radio' :
    break;

    default :
        $args['class'][] = 'form-group';
        $args['input_class'] = array('form-control', 'input-lg');
        $args['label_class'] = array('control-label');
    break;
    }

    return $args;
}