Form API focus on first input

Question

When my form load I would like to set the focus on the first field in the form. I know I can use jquery to do this by doing $('inout id').focus();. Where would I put this code so that it only runs on a certain form?

Is there a simpler way?

Updated

Using a mixture of smile's answer and clive's comment the code that got it working in the end was:

$form['#attached']['js'] = array('(function ($){$(document).ready(function() { $(".form-item-field-name input").focus()});})(jQuery);' => array( 'type' => 'inline'));

Answer 1

You can attach js only to your form. Use hook_form_alter()

function your_module_form_alter(&$form, &$form_state, $form_id) {
  if($form_id == 'my_form'){
  // Add JavaScript file
  $form['#attached']['js'] = array(drupal_get_path('module', 'your_module') . '/your_file.js');

  // Or for inline JavaScript
  $form['#attached']['js'] = array('/* some javascript here */' => array( 'type' => 'inline'));
  }
}

Answer 2

To add the HTML5 autofocus attribute from a module in D7, use this example for the user-login form. However, still not supported on iOS Safari as of this posting date.

function HOOK_form_user_login_alter(&$form, &$form_state, $form_id) {
    //should also add JS focus code for iOS Safari
    $form['name']['#attributes'] = array('autofocus' => '');
}