How can I select some JSON object having name "forecast_XXX" using XPATH\JSONPATH?

Question

I am not so into XPATH and I have the following problem.

I have this JSON object:

{
    "forecast_1": {
        "country": "Rwanda",
        "forecast_date": "2018-03-20",
        "province": "Kigali City",
        "district": "Kigali",
        "morning": {
            "min_temp": 14,
            "status": "Sun with right rain",
            "max_temp": 16,
            "humidity": "",
            "wind_direction": "",
            "wind_force": "",
            "description": "Lorem ipsum"
        },
        "afternoon": {
            "min_temp": 24,
            "status": "Dark cloud with rain",
            "max_temp": 28,
            "humidity": "",
            "wind_direction": "",
            "wind_force": "",
            "description": "Lorem ipsum"
        }
    },
    "forecast_2": {
        "country": "Rwanda",
        "forecast_date": "2018-03-25",
        "province": "Kigali",
        "district": "Kigali",
        "morning": {
            "min_temp": 21,
            "status": "Rain showers",
            "max_temp": 21,
            "humidity": "",
            "wind_direction": "",
            "wind_force": "",
            "description": "There will be heavy rain"
        },
        "afternoon": {
            "min_temp": 32,
            "status": "Rain showers",
            "max_temp": 32,
            "humidity": "",
            "wind_direction": "",
            "wind_force": "",
            "description": "There will be heavy rain with thunder"
        }
    }
}

as you can see it contains 2 "root" object identified by forecast_XXX (but can be more than 2), in the specific case I have forecast_1 and forecast_2.

So I can have a collection of JSON objects like these but there are not into a JSON array (they come from an external web service and I can not have them inside an array).

So I need an XPATH expression that identifies all these forecast_XXX objects (so I can try to iterate on these objects as if thse object were inside an array).

How can I select all these forecast_XXX objects using XPATH expression? And where can I test it? (it should exist some online tool where I put the JSON and my XPATH expression and I obtain the output)

Answer 1

For selection into JSON structures using XPath, you need XPath 3.1. (I'll leave a JsonPath answer to others.)

This use of forecast_N keys is an unfortunate way of doing the data design, but it can be handled as:

map:keys()[$json, matches('.', 'forecast_[0-9]+')]!map:get($json, .)

Assuming $json is the result of parsing the JSON input using parse-json() or json-doc().

If your XPath 3.1 engine supports higher order functions then you could also do

map:for-each($json, 
    function($k, $v){$v[matches($k, 'forecast_[0-9]+')]})