Flatten deep nested object: const nestedData = { name: 'Abc', age: '29', address: { pincode: '110011', area: 'bangalore', state: 'karnataka', location: { lat: '122.21', long: '11.21', }, phone: '1212121', }, }; Output: const op = { "nestedData_name": "Abc", "nestedData_age": "29", "nestedData_address_pincode": "110011", "nestedData_address_area": "bangalore", "nestedData_address_state": "karnataka", "nestedData_address_location_lat": "122.21", "nestedData_address_location_long": "11.21", "nestedData_address_phone": "1212121" }