Extract values from nested JSON to array using JS

Question

I have a JSON file with nested objects, I need to extract a specific key's value from each object and save to an array. No need to preserve the structure or order.

Please see JSON below. I need to extract the values of the 'text' key and have a resulting array like this ["CPUs", "AMD", "Ryzen", "intel",....]

What is the best way to achieve this?

[
   {
      "itemID":"1",
      "items":[
         {
            "itemID":"2",
            "items":[
               {
                  "itemID":"3",
                  "items":[
                     {
                        "itemID":"15",
                        "text":"Ryzen"
                     },
                     {
                        "itemID":"16",
                        "text":"Threadripper"
                     }
                  ],
                  "text":"AMD",
               },
               {
                  "itemID":"66",
                  "items":[
                     {
                        "itemID":"76",
                        "text":"i5"
                     },
                     {
                        "itemID":"77",
                        "text":"i7"
                     },
                     {
                        "itemID":"78",
                        "text":"i3"
                     }
                  ],
                  "text":"Intel"
               },
               {
                  "itemID":"70",
                  "text":"Apple"
               }
            ],
            "text":"CPUs"
         }
      ],
      "text":"computer parts"
   },
   {
      "itemID":"4",
      "items":[
         {
            "itemID":"5",
            "items":[
               {
                  "itemID":"21",
                  "text":"porsche"
               },
               {
                  "itemID":"22",
                  "text":"maserati"
               },
               {
                  "itemID":"23",
                  "text":"ferrari"
               }
            ],
            "text":"sports cars"
         }
      ],
      "text":"cars"
   }
]

Nick · Accepted Answer · 2021-05-03 13:15:37Z

1

You can write a recursive function which returns the text value at the current node, then all the text values from its child items:

const data = [{"itemID":"1","items":[{"itemID":"2","items":[{"itemID":"3","items":[{"itemID":"15","text":"Ryzen"},{"itemID":"16","text":"Threadripper"}],"text":"AMD"},{"itemID":"66","items":[{"itemID":"76","text":"i5"},{"itemID":"77","text":"i7"},{"itemID":"78","text":"i3"}],"text":"Intel"},{"itemID":"70","text":"Apple"}],"text":"CPUs"}],"text":"computer parts"},{"itemID":"4","items":[{"itemID":"5","items":[{"itemID":"21","text":"porsche"},{"itemID":"22","text":"maserati"},{"itemID":"23","text":"ferrari"}],"text":"sports cars"}],"text":"cars"}];

const extract = (arr) => arr.reduce((acc, obj) => acc.concat(obj.text, extract(obj.items || [])), [])

out = extract(data);
console.log(out);

answered May 3, 2021 at 13:15

Nick

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Comments

a.mola · Accepted Answer · 2021-05-03 13:14:03Z

Simple recursion should help to iterate through the array to get the objects with the text property

const data = [{"itemID":"1","items":[{"itemID":"2","items":[{"itemID":"3","items":[{"itemID":"15","text":"Ryzen"},{"itemID":"16","text":"Threadripper"}],"text":"AMD"},{"itemID":"66","items":[{"itemID":"76","text":"i5"},{"itemID":"77","text":"i7"},{"itemID":"78","text":"i3"}],"text":"Intel"},{"itemID":"70","text":"Apple"}],"text":"CPUs"}],"text":"computer parts"},{"itemID":"4","items":[{"itemID":"5","items":[{"itemID":"21","text":"porsche"},{"itemID":"22","text":"maserati"},{"itemID":"23","text":"ferrari"}],"text":"sports cars"}],"text":"cars"}];

function getText(item) {
  let result = [];

  if (item.text) result.push(item.text);
  for (const key in item) {
    if (item.hasOwnProperty(key) && typeof item == 'object') result.push(...getText(item[key]));
  }

  return result;
}

data.forEach(item => console.log(getText(item)));

vincent · Accepted Answer · 2021-05-04 23:59:27Z

Here is an iterative solution using object-scan. To me it's more readable and maintainable than writing a custom recursive function. But adding a dependency is obviously a tradeoff

// const objectScan = require('object-scan');

const data = [{ itemID: '1', items: [{ itemID: '2', items: [{ itemID: '3', items: [{ itemID: '15', text: 'Ryzen' }, { itemID: '16', text: 'Threadripper' }], text: 'AMD' }, { itemID: '66', items: [{ itemID: '76', text: 'i5' }, { itemID: '77', text: 'i7' }, { itemID: '78', text: 'i3' }], text: 'Intel' }, { itemID: '70', text: 'Apple' }], text: 'CPUs' }], text: 'computer parts' }, { itemID: '4', items: [{ itemID: '5', items: [{ itemID: '21', text: 'porsche' }, { itemID: '22', text: 'maserati' }, { itemID: '23', text: 'ferrari' }], text: 'sports cars' }], text: 'cars' }];

const find = objectScan(['**(^items$).text'], {
  useArraySelector: false,
  rtn: 'value'
});

console.log(find(data));
/* => [
  'cars',    'sports cars',
  'ferrari', 'maserati',
  'porsche', 'computer parts',
  'CPUs',    'Apple',
  'Intel',   'i3',
  'i7',      'i5',
  'AMD',     'Threadripper',
  'Ryzen'
] */

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

<script src="https://bundle.run/[email protected]"></script>

Disclaimer: I'm the author of object-scan

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