How to rename JSON key

Question

I have a JSON object with the following content:

[
  {
    "_id":"5078c3a803ff4197dc81fbfb",
    "email":"user1@gmail.com",
    "image":"some_image_url",
    "name":"Name 1"
  },
  {
    "_id":"5078c3a803ff4197dc81fbfc",
    "email":"user2@gmail.com",
    "image":"some_image_url",
    "name":"Name 2"
  }
]

I want to change the "_id" key to "id" so it would become

[
  {
    "id":"5078c3a803ff4197dc81fbfb",
    "email":"user1@gmail.com",
    "image":"some_image_url",
    "name":"Name 1"
  },
  {
    "id":"5078c3a803ff4197dc81fbfc",
    "email":"user2@gmail.com",
    "image":"some_image_url",
    "name":"Name 2"
  }
]

How would I do that either with Javascript, jQuery or Ruby, Rails?

Thanks.

Parse the JSON, modify the resulting data structure accordingly and convert it back to JSON. Pointers: http://stackoverflow.com/questions/4935632/how-to-parse-json-in-javascript, http://stackoverflow.com/questions/1826727/how-do-i-parse-json-with-ruby-on-rails, http://stackoverflow.com/questions/2295496/convert-javascript-array-to-json, http://stackoverflow.com/questions/3183786/how-to-convert-a-ruby-hash-object-to-json. — Felix Kling, Nov 15 '12 at 04:29

Paul · Accepted Answer · 2020-08-07T14:59:15.687

113

Parse the JSON

const arr = JSON.parse(json);

For each object in the JSON, rename the key:

obj.id = obj._id;
delete obj._id;

Stringify the result

All together:

function renameKey ( obj, oldKey, newKey ) {
  obj[newKey] = obj[oldKey];
  delete obj[oldKey];
}

const json = `
  [
    {
      "_id":"5078c3a803ff4197dc81fbfb",
      "email":"user1@gmail.com",
      "image":"some_image_url",
      "name":"Name 1"
    },
    {
      "_id":"5078c3a803ff4197dc81fbfc",
      "email":"user2@gmail.com",
      "image":"some_image_url",
      "name":"Name 2"
    }
  ]
`;
   
const arr = JSON.parse(json);
arr.forEach( obj => renameKey( obj, '_id', 'id' ) );
const updatedJson = JSON.stringify( arr );

console.log( updatedJson );

edited Aug 07 '20 at 14:59

answered Nov 15 '12 at 04:32

Paul

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7

what if I want to apply change to all _id in json? – truongnm Jun 11 '16 at 02:24
1

@truongnm loop it – Viswanath Lekshmanan Apr 04 '17 at 05:09
2

also if you want to have keys with spaces you can add it like this obj["my id"] = obj.id – catchiecop Apr 06 '17 at 09:47
**Please See Updated Answer Below (2021)** the answer from @md-shayon seems to me the simplest and [best answer](https://stackoverflow.com/a/68816259/8086910) – Pam Stums Aug 08 '22 at 14:12

score 31 · Answer 2 · edited Mar 23 '18 at 14:04

31

In this case it would be easiest to use string replace. Serializing the JSON won't work well because _id will become the property name of the object and changing a property name is no simple task (at least not in most langauges, it's not so bad in javascript). Instead just do;

jsonString = jsonString.replace("\"_id\":", "\"id\":");

edited Mar 23 '18 at 14:04

Dan Atkinson

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answered Nov 15 '12 at 04:31

evanmcdonnal

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6

And what if he will have parameters `"whereToFindIdentification":"id"` ? its never the best way. – Kamil Mar 06 '20 at 12:33
1

@Kamil the inclusion of the colon to the right in the regex, won't match your example. It implies a field named id, not a value. – Typo Oct 04 '21 at 14:06

score 26 · Answer 3 · edited May 23 '17 at 10:31

26

As mentioned by evanmcdonnal, the easiest solution is to process this as string instead of JSON,

var json = [{"_id":"5078c3a803ff4197dc81fbfb","email":"user1@gmail.com","image":"some_image_url","name":"Name 1"},{"_id":"5078c3a803ff4197dc81fbfc","email":"user2@gmail.com","image":"some_image_url","name":"Name 2"}];
    
json = JSON.parse(JSON.stringify(json).split('"_id":').join('"id":'));

document.write(JSON.stringify(json));

This will convert given JSON data to string and replace "_id" to "id" then converting it back to the required JSON format. But I used split and join instead of replace, because replace will replace only the first occurrence of the string.

edited May 23 '17 at 10:31

Community

1
1

answered Mar 16 '16 at 08:11

Stranger

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1

Thanks a lot Mr. Stranger, It really help me. – Chetan S. Choudhary Jan 06 '17 at 10:00
1

Clean, short and well explained. Great! – Andreas Aug 11 '20 at 10:24

Pylon · Answer 4 · 2022-03-08T03:04:07.377

JSON.parse has two parameters. The second parameter, reviver, is a transform function that can format the output format we want. See ECMA specification here.

In reviver function:

if we return undefined, the original property will be deleted.
this is the object containing the property being processed as this function, and the property name as a string, the property value as arguments of this function.

const json = '[{"_id":"5078c3a803ff4197dc81fbfb","email":"user1@gmail.com","image":"some_image_url","name":"Name 1"},{"_id":"5078c3a803ff4197dc81fbfc","email":"user2@gmail.com","image":"some_image_url","name":"Name 2"}]';

const obj = JSON.parse(json, function(k, v) {
    if (k === "_id") {
        this.id = v;
        return; // if return  undefined, orignal property will be removed
    }
    return v;
});

const res = JSON.stringify(obj);
console.log(res)

output:

[{"email":"user1@gmail.com","image":"some_image_url","name":"Name 1","id":"5078c3a803ff4197dc81fbfb"},{"email":"user2@gmail.com","image":"some_image_url","name":"Name 2","id":"5078c3a803ff4197dc81fbfc"}]

This seems like the most correct and clean answer to me. It deals with the problem right at the parsing stage, not ex post like all the others. It also seems like the fastest one, though some benchmarks might be necessary. — Papooch, Feb 05 '21 at 10:17

score 12 · Answer 5 · edited Jun 24 '19 at 20:25

Try this:

let jsonArr = [
    {
        "_id":"5078c3a803ff4197dc81fbfb",
        "email":"user1@gmail.com",
        "image":"some_image_url",
        "name":"Name 1"
    },
    {
        "_id":"5078c3a803ff4197dc81fbfc",
        "email":"user2@gmail.com",
        "image":"some_image_url",
        "name":"Name 2"
    }
]

let idModified = jsonArr.map(
    obj => {
        return {
            "id" : obj._id,
            "email":obj.email,
            "image":obj.image,
            "name":obj.name
        }
    }
);
console.log(idModified);

score 8 · Answer 6 · answered Jul 03 '17 at 13:51

8

If you want to rename all occurrences of some key you can use a regex with the g option. For example:

var json = [{"_id":"1","email":"user1@gmail.com","image":"some_image_url","name":"Name 1"},{"_id":"2","email":"user2@gmail.com","image":"some_image_url","name":"Name 2"}];

str = JSON.stringify(json);

now we have the json in string format in str.

Replace all occurrences of "_id" to "id" using regex with the g option:

str = str.replace(/\"_id\":/g, "\"id\":");

and return to json format:

json = JSON.parse(str);

now we have our json with the wanted key name.

answered Jul 03 '17 at 13:51

RafaelJan

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This won't work if there is a value anywhere containing the key name you are replacing, as it will replace that as well. – Carasel Nov 30 '17 at 11:42
Good point but edge case. Always need to be carefull when replacing text – RafaelJan Nov 30 '17 at 13:04

Aurelio Gualda · Answer 7 · 2019-05-07T16:23:30.090

3

Is possible, using typeScript

function renameJson(json,oldkey,newkey) {    
 return Object.keys(json).reduce((s,item) => 
      item == oldkey ? ({...s,[newkey]:json[oldkey]}) : ({...s,[item]:json[item]}),{})   
}

Example: https://codepen.io/lelogualda/pen/BeNwWJ

edited May 07 '19 at 16:23

answered Apr 29 '19 at 15:09

Aurelio Gualda

47
3

this is elegant and also saves memory. – Pam Stums Aug 08 '22 at 13:54

score 3 · Answer 8 · answered May 23 '19 at 13:36

By using map function you can do that. Please refer below code.

var userDetails = [{
  "_id":"5078c3a803ff4197dc81fbfb",
  "email":"user1@gmail.com",
  "image":"some_image_url",
  "name":"Name 1"
},{
  "_id":"5078c3a803ff4197dc81fbfc",
  "email":"user2@gmail.com",
  "image":"some_image_url",
  "name":"Name 2"
}];

var formattedUserDetails = userDetails.map(({ _id:id, email, image, name }) => ({
  id,
  email,
  image,
  name
}));
console.log(formattedUserDetails);

LukeVenter · Answer 9 · 2020-04-13T10:15:34.270

If anyone needs to do this dynamically:

const keys = Object.keys(jsonObject);

keys.forEach((key) => {

      // CREATE A NEW KEY HERE
      var newKey = key.replace(' ', '_');

      jsonObject[newKey] = jsonObject[key];
      delete jsonObject[key];
   });

jsonObject will now have the new keys.

IMPORTANT:

If your key is not changed by the replace function, it will just take it out of the array. You may want to put some if statements in there.

trojek · Answer 10 · 2020-11-18T08:42:50.950

2

If your object looks like this:

obj = {
    "_id":"5078c3a803ff4197dc81fbfb",
    "email":"user1@gmail.com",
    "image":"some_image_url",
    "name":"Name 1"
   }

Probably the simplest method in JavaScript is:

obj.id = obj._id
del object['_id']

As a result, you will get:

obj = {
    "id":"5078c3a803ff4197dc81fbfb",
    "email":"user1@gmail.com",
    "image":"some_image_url",
    "name":"Name 1"
   }

edited Nov 18 '20 at 08:42

answered Apr 03 '18 at 09:54

trojek

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score 1 · Answer 11 · answered Jun 14 '21 at 05:11

If you want replace the key of JSON object, use below logic

const student= {
  "key": "b9ed-9c1a04247482",
  "name": "Devaraju",
  "DOB" : "01/02/2000",
  "score" : "A+"
}
let {key, ...new_student} = {...student}
new_student.id= key

console.log(new_student)

score 0 · Answer 12 · answered Sep 23 '22 at 08:17

To update oldKey with a newKey in a nested json at any deeper level.

function transformKeys(object, newKey, oldKey) {
    if(Array.isArray(object)){
        object.map((item) => {
            transformKeys(item, newKey, oldKey)
        })
    }
    if(typeof object === 'object' && !Array.isArray(object)){
        Object.keys(object).forEach(key => {
            if (typeof object[key] === 'object') {
                transformKeys(object[key], newKey, oldKey)
            }
            if (key === oldKey) {
                object[newKey] = object[key]
                delete object[key]
            }
        })
    }
}

score 0 · Answer 13 · answered Dec 03 '22 at 17:12

My answer works for nested json like this,


[
  {
    "id": 1,
    "name": "1111111111",
    "children": [
      {
        "id": 2,
        "name": "2222",
      }
    ]
  },
  {
    "id": 3,
    "name": "1",
  },
]

I want replace key 'id' to 'value', and 'name' to 'label' for select componet.

Function:

function renameKeyInJson(json, keys) {
  let dataStr = JSON.stringify(json);
  keys.forEach(e => {
    dataStr = dataStr.replace(new RegExp(`"${e.oldKey}":`, "g"), `"${e.newKey}":`);
  });
  return JSON.parse(dataStr);
}

Usage:

const response = await getAll(bookId);
return renameKeyInJson(response.data, [
  {oldKey: 'name', newKey: 'label'},
  {oldKey: 'id', newKey: 'value'},
]);

Thang Tran · Answer 14 · 2023-02-11T17:12:01.213

My case:

renameJsonKey(json, oldKey, newKey) {
    Map<String, dynamic> newJson = {};
    json.forEach((key, value) {
      if (key == oldKey) {
        newJson.addAll({newKey: json[key]});
      } else {
        newJson.addAll({key: json[key]});
      }
    });
    return newJson;
  }

Change many keys:

renameJsonKeys(json, List<String> oldKeys, List<String> newKeys) {
  Map<String, dynamic> newJson = json;
  for (var i = 0; i < oldKeys.length; i++) {
    newJson = renameJsonKey(newJson, oldKeys[i], newKeys[i]);
  }
  return newJson;
}

score -1 · Answer 15 · edited Feb 11 '18 at 09:00

If you want to do it dynamically, for example, you have an array which you want to apply as a key to JSON object:

your Array will be like :

var keys = ["id", "name","Address","Phone"] // The array size should be same as JSON Object keys size

Now you have a JSON Array like:

var jArray = [
  {
    "_id": 1,
    "_name": "Asna",
    "Address": "NY",
    "Phone": 123
  },
  {
    "_id": 2,
    "_name": "Euphoria",
    "Address": "Monaco",
    "Phone": 124
  },
  {
    "_id": 3,
    "_name": "Ahmed",
    "Address": "Mumbai",
    "Phone": 125
  }
]

$.each(jArray ,function(pos,obj){
    var counter = 0;
    $.each(obj,function(key,value){
        jArray [pos][keys[counter]] = value;
        delete jArray [pos][key];
        counter++;
    })  
})

Your resultant JSON Array will be like :

[
  {
    "id": 1,
    "name": "Asna",
    "Address": "NY",
    "Phone": 123
  },
  {
    "id": 2,
    "name": "Euphoria",
    "Address": "Monaco",
    "Phone": 124
  },
  {
    "id": 3,
    "name": "Ahmed",
    "Address": "Mumbai",
    "Phone": 125
  }
]

score -1 · Answer 16 · answered Apr 26 '22 at 19:05

For a more flexible solution for renaming a key in an object,

Usage:

jsondata = renameKey(jsondata,"_id","id");

Function:

function renameKey(data,oldname,newname)
{
    for (let i = 0; i < data.length; i++) {
        let element = data[i];
        element[newname] = element[oldname];
        delete element[oldname];
    }
    return data;
}

if you need the keys to stay in the same order (like i did) here is a messy solution that I'm sure is poorly optimized.

function renameKey(data,oldname,newname)
{
    for (let i = 0; i < data.length; i++)
    {
        let element = data[i];
        let info = Object.keys(data[i]);

        for (let ii = 0; ii < info.length; ii++)
        {

            let key = info[ii];
            if (key !== oldname)
            {
                let skey = key + "~"; //make temporary key
                element[skey] = element[key]; //copy values to temp key
                delete element[key]; //delete old key
                element[key] = element[skey]; //copy key back to orginal name, preserving its position.
                delete element[skey]; //delete temp key
            }
            else
            {
                element[newname] = element[key];
                delete element[key];
            }
        }
    }
    return data;
}

How to rename JSON key

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