You could use Array.map instead to map this clearer:

```javascript
urlList = memcachedURL.split( ',' ).map( function( host ) {
  var hostElems = host.split( ':' ),
  hostname = hostElems[ 0 ] || 'localhost',
  port = hostElems[ 1 ] || 11211;
  return hostname + ':' + port;
});
```