How to get the length of a JSON array using JSONPath? - json

Question

If I have JSON document like this
[
{
"number" : "650-462-9154",
"type" : "main"
},
{
"number" : "650-462-1252",
"type" : "fax"
}
]
What JSONPath can I use to get the array length (which is 2), without hardcoding any property values?
Using the tool I have, here is some examples they gave, which doesn't help me figure out what value I need.
[
{
"type": "add",
"id": "tt0484562",
"version": 1,
"lang": "en",
"fields": {
"title": "The Seeker: The Dark Is Rising",
"director": "Cunningham, David L.",
"genre": ["Adventure","Drama","Fantasy","Thriller"],
"actor": ["McShane, Ian","Eccleston, Christopher","Conroy, Frances",
"Crewson, Wendy","Ludwig, Alexander","Cosmo, James",
"Warner, Amelia","Hickey, John Benjamin","Piddock, Jim",
"Lockhart, Emma"]
}
},
{
"type": "delete",
"id": "tt0484575",
"link_ref": null,
"version": 2
}
]
$.[0].genre ---> 0
$.[0].fields.genre ---> 1
$.[0].fields.genre[*] ---> 4
$.[*].type ---> 2
$.[1].link_ref ---> 1

Answer 1

You can get the length of the array from the first example by using the .length() function like this :
$.length
That should return something like this:
[
2
]
As for the second example, you can access any array keys using regular dot notation ($.node1.node2.node3) and call the length() function on the node key you wish to get the length of. For example, if you wanted to get the number of values in the actor array you could do something like:
$..actor.length
Which will return something like this:
[
10
]
Tested on https://codebeautify.org/jsonpath-tester and http://jsonpath.com/ .
You can find more functions in the jsonpath github repo.