Extract New Fields
Extracts only new fields that exist in an updated object but not in a base object, including nested fields.
Import
import { extractNewFields } from 'nhb-toolbox';
Usage
Basic Example
const original = { name: 'John' };
const updated = { name: 'John', age: 30 };
const newFields = extractNewFields(original, updated); // { age: 30 }
Nested Objects
const configV1 = { theme: { dark: true } };
const configV2 = { theme: { dark: true, colors: ['blue'] } };
const changes = extractNewFields(configV1, configV2); // { theme: { colors: ['blue'] } }
API Reference
Type Parameters
| Name | Description |
|---|---|
T | Base object type |
U | Updated object type |
Parameters
| Name | Type | Description |
|---|---|---|
baseObject | T | Original object for comparison |
updatedObject | FlattenPartial<T> & FlattenPartial<U> | Object containing potential new fields |
Returns
FlattenPartial<U>: New fields that didn't exist in base object.
Examples
Detecting New Configuration
const oldSettings = { volume: 50 };
const newSettings = { volume: 50, notifications: true };
extractNewFields(oldSettings, newSettings); // { notifications: true }
Deep Nested Comparison
const v1 = { user: { profile: { name: 'Alice' } } };
const v2 = { user: { profile: { name: 'Alice', age: 28 } } };
extractNewFields(v1, v2); // { user: { profile: { age: 28 } } }
Limitations
- Value Changes: Won't detect if existing fields have new values
- Circular References: May cause stack overflow with circular structures for deeply nested objects and arrays
- Type Strictness: Requires both objects to be structurally compatible
Type Definitions
type GenericObject = Record<string, any>;
type FlattenPartial<T> = Partial<{ [K in keyof T]: T[K] }>;
When to Use
- Comparing API response changes
- Detecting new configuration options
- State management diffing
- Migration scenario analysis