mergeDeep#

Recursively deep merges two objects, with properties from the source object overwriting those from the target object. Supports symbol keys and preserves property descriptors. Arrays are merged by index.

Usage Scenarios#

• Nested Object Merging: Combine deeply nested objects while preserving their structure.
• Configuration Management: Merge default configurations with user overrides.
• State Management: Combine complex state objects in immutable updates.

Examples#

import { mergeDeep } from 'funtool';

const a = { 
  user: { 
    name: 'Alice', 
    hobbies: [{ sport: 'tennis' }] 
  } 
};
const b = { 
  user: { 
    age: 30, 
    hobbies: [{ level: 'pro' }] 
  } 
};
const result = mergeDeep(a, b);
// result: { 
//   user: { 
//     name: 'Alice', 
//     age: 30, 
//     hobbies: [{ sport: 'tennis', level: 'pro' }] 
//   } 
// }

Signature#

function mergeDeep<T extends object, U extends object>(target: T, source: U): T & U

Parameters#

• target (T extends object): The target object to receive properties.
• source (U extends object): The source object to copy properties from.

Returns#

• (T & U): A new object with deeply merged properties.