How to modify key values in an object with JavaScript and remove the underscore?

In JavaScript, you can modify object keys to remove underscores and convert them to camelCase using regular expressions combined with Object.fromEntries() and Object.entries().

Syntax

const camelCaseKey = str => str.replace(/(_)(.)/g, (_, __, char) => char.toUpperCase());
const newObject = Object.fromEntries(
    Object.entries(originalObject).map(([key, value]) => [camelCaseKey(key), value])
);

Example

// Function to convert underscore keys to camelCase
var underscoreSpecifyFormat = str => str.replace(/(_)(.)/g, (_, __, v) => v.toUpperCase());

// Original object with underscore keys
var JsonObject = { 
    first_Name_Field: 'John', 
    last_Name_Field: 'Smith' 
};

// Transform the object keys
var output = Object.fromEntries(
    Object.entries(JsonObject).map(([key, value]) => [underscoreSpecifyFormat(key), value])
);

console.log("The JSON Object=");
console.log(output);

The JSON Object=
{ firstNameField: 'John', lastNameField: 'Smith' }

How It Works

The transformation process involves three key steps:

• Object.entries() converts the object into an array of [key, value] pairs
• The map() method transforms each key using the regex pattern /(_)(.)/g
• Object.fromEntries() reconstructs the object with the modified keys

Multiple Underscore Example

var convertToCamelCase = str => str.replace(/(_)(.)/g, (_, __, char) => char.toUpperCase());

var complexObject = {
    user_first_name: 'Alice',
    user_last_name: 'Johnson',
    account_creation_date: '2023-01-15',
    is_active_user: true
};

var result = Object.fromEntries(
    Object.entries(complexObject).map(([key, value]) => [convertToCamelCase(key), value])
);

console.log(result);

{
  userFirstName: 'Alice',
  userLastName: 'Johnson',
  accountCreationDate: '2023-01-15',
  isActiveUser: true
}

Conclusion

Use Object.fromEntries() with Object.entries() and regex replacement to efficiently transform object keys from underscore notation to camelCase. This approach preserves all values while modifying only the key structure.