Adding JavaScript just to one node I have added scripts[] = js/add_property.js to my .info file which works perfectly. 

That loads the JavaScript for every page though, so how do you do it so that it only loads for the .tpl that it is used in?
If you want to add the Javascript to a single node, you might also implement hook_node_view:

&lt;?php
function my_module_node_view($node, $viewmode, $langcode)
{
  if ($node-&gt;nid == MY_NODE_ID) {
    $node-&gt;content['#attached']['js'][] = array
    (
      'type' =&gt; 'file',
      'data' =&gt; drupal_get_path('module', 'my_module') . 'js/add_property.js',
    );
  }
}
?&gt;


(Solution adapted from https://www.drupal.org/node/1993228).