Attach JS to a drupal block

block.php

<?php

//put this in hook_bock_view

$block['content'] = array(
  ///....
  '#attached' => array(
      'css' => array(
        drupal_get_path('module', 'mymodule') . '/css/mymodule.css',
      ),
      'js' => array(
        drupal_get_path('module', 'mymodule') . '/js/mymodule.js',
    ),
  ),
);