'How to count JSON Objects in array filtered by attribute of the object by JSONPath

I'm writing a JSONPath expression that counts objects in an array while filtering by one of the field of the object.

Input JSON taken from http://jsonpath.herokuapp.com/

{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    },
    "expensive": 10
}

And my expression that extracts object where "category" is "fiction".

$.store.book[?(@.category == "fiction")]

The output is as expected.

[
   {
      "category" : "fiction",
      "author" : "Evelyn Waugh",
      "title" : "Sword of Honour",
      "price" : 12.99
   },
   {
      "category" : "fiction",
      "author" : "Herman Melville",
      "title" : "Moby Dick",
      "isbn" : "0-553-21311-3",
      "price" : 8.99
   },
   {
      "category" : "fiction",
      "author" : "J. R. R. Tolkien",
      "title" : "The Lord of the Rings",
      "isbn" : "0-395-19395-8",
      "price" : 22.99
   }
]

So far so good. What I would like to achieve is to count the number of objects in the array. In this case 3. I tried this expression:

$.store.book[?(@.category == "fiction")].length()

The output is not what I expected.

[
   4,
   5,
   5
]

The below didn't work either

$.store[?(@.book[*].category == "fiction")].length()

How do I count the number of elements in the array? If I use jq it could be written as

[.store.book[] | select (.category == "fiction")] | length
javajsonpath


Solution 1:[1]

Very late for the answer but I came across this scenario recently and managed to get the number of object inside the array using below JsonPath query as per the JSON provided in question:

$.length($.store.book[?(@.category == "fiction")].length())

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution Source
Solution 1 Reyan Chougle

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