Convert returned JSON Object Properties to (lower first) camelCase

Question

I have JSON returned from an API like so:

Contacts: [{ GivenName: "Matt", FamilyName: "Berry" }]

To keep this consistent

Answer 1

You can do this with this recursive function (with lodash and ES6):

import { camelCase } from 'lodash';

const camelizeKeys = (obj) => {
  if (Array.isArray(obj)) {
    return obj.map(v => camelizeKeys(v));
  } else if (obj !== null && obj.constructor === Object) {
    return Object.keys(obj).reduce(
      (result, key) => ({
        ...result,
        [camelCase(key)]: camelizeKeys(obj[key]),
      }),
      {},
    );
  }
  return obj;
};

Test:

const obj = {
  'FirstName': 'John',
  'LastName': 'Smith',
  'BirthDate': new Date(),
  'ArrayTest': ['one', 'TWO', 3],
  'ThisKey': {
    'This-Sub-Key': 42
  }
}

console.log(JSON.stringify(camelizeKeys(obj)))

Output:

{  
   "firstName": "John",
   "lastName": "Smith",
   "birthDate": "2018-05-31T09:03:57.844Z",
   "arrayTest":[  
      "one",
      "TWO",
      3
   ],
   "thisKey":{  
      "thisSubKey": 42
   }
}

Answer 2

I needed a generic method that accepted an array or object. This is what I'm using (I borrowed KyorCode's firstToLower() implementation):

function convertKeysToCamelCase(obj) {
    if (!obj || typeof obj !== "object") return null;

    if (obj instanceof Array) {
        return $.map(obj, function(value) {
            return convertKeysToCamelCase(value);
        });
    }

    var newObj = {};
    $.each(obj, function(key, value) {
        key = key.charAt(0).toLowerCase() + key.slice(1);
        if (typeof value == "object" && !(value instanceof Array)) {
          value = convertKeysToCamelCase(value);
        }
        newObj[key] = value;
    });

    return newObj;
};

Example calls:

var contact = { GivenName: "Matt", FamilyName:"Berry" };

console.log(convertKeysToCamelCase(contact));
// logs: Object { givenName="Matt", familyName="Berry"}

console.log(convertKeysToCamelCase([contact]));
// logs: [Object { givenName="Matt", familyName="Berry"}]

console.log(convertKeysToCamelCase("string"));
// logs: null

console.log(contact);
// logs: Object { GivenName="Matt", FamilyName="Berry"}

Answer 3

To change a plain object's keys from snake_case to camelCase recursively try the following
(which uses Lodash):

function objectKeysToCamelCase(snake_case_object) {
  var camelCaseObject = {};
  _.forEach(
    snake_case_object,
    function(value, key) {
      if (_.isPlainObject(value) || _.isArray(value)) {     // checks that a value is a plain object or an array - for recursive key conversion
        value = objectKeysToCamelCase(value);               // recursively update keys of any values that are also objects
      }
      camelCaseObject[_.camelCase(key)] = value;
    }
  )
  return camelCaseObject;
};

test in this PLUNKER

Note: also works recursively for objects within arrays

Answer 4

If you would use lodash instead of underscore, this would do:

_.mapKeys(obj, (v, k) => _.camelCase(k))

This would convert both TitleCase and snake_case to camelCase. Note that it is not recursive though.

Answer 5

Using lodash, you can do it like this:

export const toCamelCase = obj => {
  return _.reduce(obj, (result, value, key) => {
    const finalValue = _.isPlainObject(value) || _.isArray(value) ? toCamelCase(value) : value;
    return { ...result, [_.camelCase(key)]: finalValue };
  }, {});
};

Answer 6

This solution based on the plain js solution above, uses loadash and Keeps an array if passed as a parameter and Only change the Keys

function camelCaseObject(o) {
    let newO, origKey, value
    if (o instanceof Array) {
        newO = []
        for (origKey in o) {
            value = o[origKey]
            if (typeof value === 'object') {
                value = camelCaseObject(value)
            }
            newO.push(value)
        }
    } else {
        newO = {}
        for (origKey in o) {
            if (o.hasOwnProperty(origKey)) {
                newO[_.camelCase(origKey)] = o[origKey]
            }
        }
    }
    return newO
}

// Example
const obj = [
{'my_key': 'value'},
 {'Another_Key':'anotherValue'},
 {'array_key':
   [{'me_too':2}]
  }
]
console.log(camelCaseObject(obj))

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>