title: How include mask in the Woocommerce fields? E.g. Phone: (99) 9999-9999
body: <p>According to the WC docs, if I want to add a new field in the checkout area I should write the following code in <code>functions.php:</code></p>
  
  <pre><code>/* Add the field to the checkout*/
  add_action('woocommerce_after_order_notes', 'my_custom_checkout_field');
  
  function my_custom_checkout_field( $checkout ) {
  echo '&lt;div id="my_custom_checkout_field" class="my_new_field"&gt;&lt;h2&gt;' . __('My Field') . '&lt;/h2&gt;';
  
  woocommerce_form_field( 'my_field_name', array(
      'type'          =&gt; 'text',
      'class'         =&gt; array('my-field-class form-row-wide'),
      'label'         =&gt; __('Fill in this field'),
      'placeholder'   =&gt; __('Enter something'),
  ), $checkout-&gt;get_value('my_field_name'));
  
  echo '&lt;/div&gt;';
  }
  </code></pre>
  
  <p>If I want to edit fields Label or Placeholder, then I should use also this other code in <code>functions.php</code>:</p>
  
  <pre><code>// Hook in
  add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );
  
  // Our hooked in function - $fields is passed via the filter!
  function custom_override_checkout_fields( $fields ) {
  $fields['order']['order_comments']['placeholder'] = 'My new placeholder';
  $fields['order']['order_comments']['label'] = 'My new label';
  
  return $fields;
  }
  </code></pre>
  
  <p>Considering above codes, <strong>how can I include field masks in the Woocommerce?</strong>  </p>
  
  <p>I've done this before in my html site with Jquery (out of Wordpress) but I can't figure out how to do it in the Woocommerce. </p>
  
  <p>Fyg, I've already tried the plugin "WooCommerce Extra Checkout Fields for Brazil" and it didn't work properly.</p>