Function Extensions

Function Extensions

Function Extensions in RFC 9535

Five typed functions are standard: length() of a string, array or object; count() of a nodelist; match() and search(), which test an I-Regexp (RFC 9485) against the whole string or any part of it; and value(), which unwraps a single-node nodelist.

The standard functions on books and the first 12 ordersJavaScript

import itertools, json
import jsonpath
books = json.load(open("data/books.json", encoding="utf-8"))
orders = [json.loads(s) for s in itertools.islice(open("data/orders.jsonl"), 12)]
for query, data in [("$.books[?length(@.title) > 22].id", books),
                    ("$.books[?match(@.genre, 'Science')].id", books),
                    ("$.books[?search(@.genre, 'Science')].id", books),
                    ("$[?count(@.items[*]) == 3].order_id", orders),
                    ("$[?value(@.items[*].qty) == 2].order_id", orders)]:
    print(f"{query:52} {jsonpath.findall(query, data)}")

Output

$.books[?length(@.title) > 22].id                    [2, 4, 5]
$.books[?match(@.genre, 'Science')].id               []
$.books[?search(@.genre, 'Science')].id              [5]
$[?count(@.items[*]) == 3].order_id                  [2, 5]
$[?value(@.items[*].qty) == 2].order_id              [9]

match is anchored at both ends, so 'Science' misses "Science Fiction". value() yields Nothing for several nodes, so the last query keeps only single-line orders.

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