function that makes a function that only calls once

once.js

// do cb only once
function do_once(cb) {
  var has_called = false;
  // the function that is returned
  return function () {
    if(!has_called) {
      cb.apply(arguments);
      has_called = true;
    }
  }
}

// usage example
process.once('SIGINT', do_once(function (conn) { conn.close(); }))