Drupal Module - add js

gistfile1.php

<?php
function ds_maps_preprocess_page(&$variables) {
  //dpm("ds_maps_preprocess_page");
  if (isset($variables['node']) && $variables['node']->type == 'map_geojson') {
    //dpm("map_geojson");
    // Add js
    drupal_add_js(drupal_get_path('module', 'ds_maps') . '/ds_maps.js');
    $variables['scripts'] = drupal_get_js();
  }
}