如何在 json 对象数组中提取深嵌套和浅嵌套字段

Question

Let's say I have this json object:

{
    "lotOfJson": [
    {
        "value": "someName",
        "property": "name",
        "children": [],
        "constraints": {
            "IsValidName": "name someName isn't valid"
        }
    },
    {
        "value": [
            {
                "id": "firstBadId"
            },
            {
                "id": "secondBadId"
            }
        ],
        "property": "listOfIds",
        "children": [
            {
                "value": {
                    "id": "firstBadId"
                },
                "property": "0",
                "children": [
                    {
                        "value": "firstBadId",
                        "property": "id",
                        "children": [],
                        "constraints": {
                            "badIdError": "This Id is bad!"
                        }
                    }
                ]
            },
            {
                "value": {
                    "id": "secondBadId"
                },
                "property": "1",
                "children": [
                    {
                        "value": "secondBadId",
                        "property": "id",
                        "children": [],
                        "constraints": {
                            "badIdError": "This Id is bad"
                        }
                    }
                ]
            }
        ]
    }
]

}

This array can have deeply nested JSON--there's no way of knowing how deep.

Whenever there's a block that looks like:

"value": "",
"property": "",
"children": [],
"constraints": {
    "": ""
}

I want to extract the values for value , property and constraints and save them in an array. For my "lotsOfJson" example above, this would look like: ["someName", "name", "name SomeName isn't valid", "firstBadId, "id", "This Id is bad!", "secondBadId, "id", "This Id is bad!"]

So I'm only extracting the value, property and constraints when they are parallel like in the block right above.

I could agnostically extract all the value , property and constraints that are in the JSON array using an iterator for instance, but is there a way to extract them only when the appear parallel to each other?

Answer 1

You could create recursive function for this using for...in loop and only add to the result when the current object have no elements in the children array.

 const data = [{"value":"someName","property":"name","children":[],"constraints":{"IsValidName":"name someName isn't valid"}},{"value":[{"id":"firstBadId"},{"id":"secondBadId"}],"property":"listOfIds","children":[{"value":{"id":"firstBadId"},"property":"0","children":[{"value":"firstBadId","property":"id","children":[],"constraints":{"badIdError":"This Id is bad!"}}]},{"value":{"id":"secondBadId"},"property":"1","children":[{"value":"secondBadId","property":"id","children":[],"constraints":{"badIdError":"This Id is bad"}}]}]}] function extract(data, fields) { let result = [] for (let i in data) { if (typeof data[i] == 'object') { result.push(...extract(data[i], fields)) } if (data.children && !data.children.length) { if (fields.includes(i)) { result = result.concat( typeof data[i] == 'object' ? Object.values(data[i]) : data[i] ) } } } return result; } const result = extract(data, ['property', 'value', 'constraints']) console.log(result)