Get unique keys from Json file NodeJs

Question

I have an json data like this

[
  {
    "Name": "User1",
    "primaryRegion": "US"
  },
  {
    "Name": "user2",
    "primaryRegion": "US"
  },
  {
    "Name": "user3",
    "primaryRegion": "US"
  },
  {
    "Name": "user4",
    "primaryRegion": "US"
  },
  {
    "Name": "user5",
    "primaryRegion": "US"
  }
]

I just want to get the unique value of keys (Json Headers) in an array like this:

["Name", "primaryRegion"]

I tried below code but not getting expected result:

let jsonData = JSON.parse(fs.readFileSync('./test/sampleData1.json', 'utf8'));

console.log("JSON Fields---", Object.keys(jsonData));

It gives below output:

JSON Fields--- [
  '0', '1', '2',
  '3', '4'
]

Does this answer your question? Get unique keys from multiple objects — VLAZ
– VLAZ, Commented Nov 22, 2023 at 14:31

Alexander Nenashev · Accepted Answer · 2023-11-23 04:48:40Z

1

Use Array::reduce() to collect your object keys in a Set:

console.log(...jsonData.reduce((set, item) => (Object.keys(item).forEach(key => set.add(key)), set), new Set));

<script>
const jsonData = [
  {
    "Name": "User1",
    "primaryRegion": "US"
  },
  {
    "Name": "user2",
    "primaryRegion": "US"
  },
  {
    "Name": "user3",
    "primaryRegion": "US"
  },
  {
    "Name": "user4",
    "primaryRegion": "US"
  },
  {
    "Name": "user5",
    "primaryRegion": "US"
  }
]
</script>

answered Nov 23, 2023 at 4:48

Alexander Nenashev

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Comments

Azat Antonyan · Accepted Answer · 2023-11-22 13:56:06Z

0

will be very happy to help you.

Instead of Object.keys(jsonData), you should use Object.keys(jsonData.reduce((obj, field) => ({...obj, ...field}), {}))

Since your json file is an array and Object.keys return the keys of the object (in JavaScript array is an object too and its keys are indexes (0, 1, 2 , ...) thats why you have in your array numbers ['0', '1', '2', '3', '4' ]

In my example, I'm accumulating the array of objects into single object (with reduce), and receiving keys from it with Object.keys

answered Nov 22, 2023 at 13:56

Azat Antonyan

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Comments

Tyler2P · Accepted Answer · 2023-11-22 16:32:55Z

The json data is an array of objects, so if you have at least one object in the array, and if all properties are the same on each object item, you can simply get the keys of the first at jsonData[0]:

if (jsonData.length > 0)
  console.log("JSON Fields---", Object.keys(jsonData[0]));

But if you have different keys on some of the objects, and you want to find out each of them, you have to iterate the array of objects, and add the key to a separate array [keys] when it is not included on that [keys] array...

let textData = '[ { "Active": "true", "Name": "User1", "primaryRegion": "US" }, { "Name": "user2", "primaryRegion": "US" }, { "Name": "user3", "primaryRegion": "US" }, { "Name": "user4", "primaryRegion": "US" }, { "Name": "user5", "primaryRegion": "US", "Currency": "USD" } ]';
let jsonData = JSON.parse(textData);

let keys = []
jsonData.forEach(element => {
  Object.keys(element).forEach(key => {
    if (!keys.includes(key))
      keys.push(key);
  })
});

console.log("JSON Fields---", keys);

Selaka Nanayakkara · Accepted Answer · 2023-11-23 04:53:43Z

0

You can use Object.keys() to achieve the following :

Refor the below code for reference:

const data = [
  {
    "Name": "User1",
    "primaryRegion": "US"
  },
  {
    "Name": "user2",
    "primaryRegion": "US"
  },
  {
    "Name": "user3",
    "primaryRegion": "US"
  },
  {
    "Name": "user4",
    "primaryRegion": "US"
  },
  {
    "Name": "user5",
    "primaryRegion": "US"
  }
];


function getUniqueKeys(data) {
  const uniqueKeys = new Set();

  data.forEach(item => {
    Object.keys(item).forEach(key => {
      uniqueKeys.add(key);
    });
  });

  return Array.from(uniqueKeys);
}

const uniqueKeys = getUniqueKeys(data);
console.log(uniqueKeys);

answered Nov 23, 2023 at 4:53

Selaka Nanayakkara

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