从 JSON 嵌套 object 键中获取值

Question

I'm trying to write a function gets a key ( string ) and returns values of it if it exists in the JSON.

Received JSON:

[
  {
    "some_key1": [
      {"key": "value1"},
      {"key": "value2"},
      {"key": "value3"}
    ]
  },
  {
    "some_key2": [
      {"key": "value4"},
      {"key": "value5"},
      {"key": "value6"}
    ]
  },
  {
    "default_val": [
      {"key": "value7"},
      {"key": "value8"},
      {"key": "value9"}
    ]
  }
]

The structure looks like this and the only thing that might vary is the number of inner objects.

Function that would return the array :

interface InnerObject {
    key: string;
}

const getValues = (key = "default_val"): InnerObject[] => {
    /* working code */
}

Example expected output:

> getValues("some_key2");
[{"key": "value4"},{"key": "value5"},{"key": "value6"}]
> getValues();
[{"key": "value7"},{"key": "value8"},{"key": "value9"}]

Any elegant solutions?

Answer 1

Same solution as Nick, but with find to return object directly:

 const data = [ { "some_key1": [ {"key": "value1"}, {"key": "value2"}, {"key": "value3"} ] }, { "some_key2": [ {"key": "value4"}, {"key": "value5"}, {"key": "value6"} ] }, { "default_val": [ {"key": "value7"}, {"key": "value8"}, {"key": "value9"} ] } ]; const getValues = (key = 'default_val') => data.find(o => Object.keys(o)[0] == key); console.log(getValues('some_key2')); console.log(getValues());

Answer 2

You could use Array.filter with a test that the key of the object is the same as the passed parameter (or default_val if one is not passed):

 const data = [ { "some_key1": [ {"key": "value1"}, {"key": "value2"}, {"key": "value3"} ] }, { "some_key2": [ {"key": "value4"}, {"key": "value5"}, {"key": "value6"} ] }, { "default_val": [ {"key": "value7"}, {"key": "value8"}, {"key": "value9"} ] } ]; const getValues = (key = 'default_val') => data.filter(o => Object.keys(o)[0] == key); console.log(getValues('some_key2')); console.log(getValues());

This code will return multiple values if there is more than one value with the same search key. If not, it's more efficient to use Array.find as described in some of the other answers.

Answer 3

That structure is not ideal for searching. Why not convert it to a better structure first, and use that for the searching?

Something like this might do:

 const makeSearcher = (input, obj = Object.assign (...input)) => (key) => obj [key] || obj.default_val const input = [{some_key1: [{key: "value1"}, {key: "value2"}, {key: "value3"}]}, {some_key2: [{key: "value4"}, {key: "value5"}, {key: "value6"}]}, {default_val: [{key: "value7"}, {key: "value8"}, {key: "value9"}]}] const search = makeSearcher (input) console.log (search ('some_key2')) console.log (search ())

This assumes there is only one object with a given key. If not, I would look to Nick's solution.

While this is an O (1) search function, no logical answer to this is likely to be more than O (n) , so I don't really think performance is likely to be a big issue either way.

Answer 4

This will do:

const getValues = (key = "default_val"): InnerObject[] => {
  return data.find(item => item[key])[key];
};

Answer 5

Here is a more generic solution using object-scan

The main advantage is that it's very easy to target eg deeper keys and multiple keys.

 // const objectScan = require('object-scan'); const myData = [{ some_key1: [{ key: 'value1' }, { key: 'value2' }, { key: 'value3' }] }, { some_key2: [{ key: 'value4' }, { key: 'value5' }, { key: 'value6' }] }, { default_val: [{ key: 'value7' }, { key: 'value8' }, { key: 'value9' }] }]; const find = (data, key) => objectScan([key], { reverse: false, rtn: 'value' })(data) console.log(find(myData, '[*].some_key2[*]')); // => [ { key: 'value4' }, { key: 'value5' }, { key: 'value6' } ]

 .as-console-wrapper {max-height: 100%;important: top: 0}

 <script src="https://bundle.run/object-scan@13.8.0"></script>

Disclaimer : I'm the author of object-scan