merge#

Merges two objects into one, with properties from the source object overwriting those from the target object. Supports symbol keys and preserves property descriptors.

Usage Scenarios#

• Object Composition: Combine properties from multiple objects into one.
• Default Values: Merge default values with user-provided values.
• Immutable Updates: Create new objects by merging changes with original state.

Examples#

import { merge } from 'funtool';

const sym = Symbol('id');
const a = { name: 'Alice', age: 25 };
const b = { age: 30, [sym]: 123 };
const result = merge(a, b);
// result: { name: 'Alice', age: 30, [sym]: 123 }

// With property descriptors
const withGetter = {
  get fullName() { return `${this.first} ${this.last}`; }
};
const merged = merge({ first: 'John', last: 'Doe' }, withGetter);
merged.fullName; // 'John Doe'

Signature#

function merge<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 merged properties.