Skip to main content

Pick Object Fields By Condition

Creates a new object containing only the properties that satisfy a given condition.

Import​

// Main function
import { pickObjectFieldsByCondition } from 'nhb-toolbox';

// Alias also available:
import { pickFieldsByCondition } from 'nhb-toolbox';

Function Signature(s)​

function pickObjectFieldsByCondition<T extends GenericObject>(
  source: T,
  condition: (key: keyof T, value: T[keyof T]) => boolean
): Partial<T>

Usage​

Basic Usage​

const user = {
  id: 1,
  name: 'John',
  email: 'john@example.com',
  age: 30,
  isAdmin: false
};

// Pick only string fields
const stringFields = pickObjectFieldsByCondition(
  user,
  (key, value) => typeof value === 'string'
);
// Returns { name: 'John', email: 'john@example.com' }

API Reference​

Type Parameters​

NameDescription
TType of source object

Parameters​

NameTypeDescription
sourceTSource object to pick from
condition(key: keyof T, value: T[keyof T]) => booleanFunction that determines if a property should be picked

Returns​

Partial<T>: New object containing only the properties that satisfy the condition

Key Features​

  1. Flexible Filtering: Condition can be based on key, value, or both
  2. Type Safe: Maintains TypeScript typing
  3. Non-Destructive: Creates new object without modifying original
  4. Deep Inspection: Can evaluate both keys and values

Examples​

Pick Non-Null Values​

const data = {
  title: 'Document',
  content: null,
  author: 'Jane',
  createdAt: undefined
};

pickObjectFieldsByCondition(data, (key, value) => value != null);
// Returns { title: 'Document', author: 'Jane' }

Pick Numeric Fields​

const product = {
  id: 101,
  name: 'Laptop',
  price: 999.99,
  inStock: true
};

pickObjectFieldsByCondition(
  product,
  (key, value) => typeof value === 'number'
);
// Returns { id: 101, price: 999.99 }

Key-Based Selection​

const config = {
  apiUrl: 'https://api.example.com',
  timeout: 5000,
  retryCount: 3,
  debugMode: false
};

pickObjectFieldsByCondition(
  config,
  (key) => key.toString().endsWith('Count') || key.toString().endsWith('Mode')
);
// Returns { retryCount: 3, debugMode: false }

Limitations​

  1. Shallow Only: Doesn't recursively inspect nested objects
  2. No Dot Notation: Can't filter nested properties by path
  3. Performance: Slower than pickFields for simple key selection
  • Filtering object properties by type
  • Removing null/undefined values
  • Selecting fields based on complex conditions
  • Data cleaning and normalization
  • Creating view-specific object subsets

Aliases​

This function is also exported as:

  • pickFieldsByCondition