the current template operators used for ecoding are a bit too opaque imho:

json_encode => works on arrays, but probably unexpected results on template objects
xml_encode => same as above
node_encode => too hardcoded in php

plus they seem not to take their params via the pipe, which is imho the best thing about template operators, $value | transform ( $trandformationdetails ) being the guiding pattern

having played around extensively with transforming objects to json/xml (see the ggxmlview extension), I think we can come up with something more useful, general and simple at the same time:

$value | obj_encode( $style='json', $depth=1, $attributes_filter=array() )

- $style mandates the type of output

- the recursive descent is done the same way that the 'attribute' operator does: iterating over $value's attribute() methods, ie. it does not iterate over the object as it is seen from php but it iterates over the object as it is seen from template code

- $depth works as limiter, the same way that the 'attribute' operator does

- the 'attributes' array allows the user to cherry pick the attributes he wants to have in the output. If not specified, all attributes are shown, otherwise only the attributes whose name appears in the list

- if $value is an array or a scalar value, the encoding is done properly, unlike the current 'attribute' template operator

With this simple operator we can
- encode all template objects we want, not just nodes, not just objects
- allow encodings that only show a bit of data and not all of it
- allow js objects to be built at 0 cost that are specular images of template objects, which is excellent for developers (no new api to be learned)
- ...
- profit!