# @stackline/deepmerge full reference

Package: @stackline/deepmerge
License: MIT
Runtime dependencies: 0
Node.js: 14.17+
TypeScript tested: 3.9, 4.7, 4.9, 5.9, 6.0, 7.0

## Installation

npm install @stackline/deepmerge

To preserve existing imports:

npm install deepmerge@npm:@stackline/deepmerge

## ESM

import merge from '@stackline/deepmerge';
const result = merge(target, source, options);

Named exports: deepmerge, all, isMergeableObject, UnsafeKeyError,
DeepMergeLimitError.

## CommonJS

const merge = require('@stackline/deepmerge');
const result = merge(target, source, options);

Static helpers are available as merge.all, merge.isMergeableObject,
merge.UnsafeKeyError, and merge.DeepMergeLimitError.

## Options

- arrayMerge(targetArray, sourceArray, options): customize arrays.
- clone: true by default; false preserves nested references.
- customMerge(key, options): select a property-specific merge callback.
- isMergeableObject(value): select traversable values.
- onUnsafeKey: "skip" by default or "throw".
- maxDepth: 1000 by default.
- maxKeys: 100000 by default.

## Security

The keys __proto__, prototype, and constructor are filtered in source and
target objects before values are read. Accepted keys are written as own data
properties. Own enumerable string and symbol keys are processed; inherited and
non-enumerable keys are not copied. Options callbacks are trusted executable
code and must not come from untrusted input.

## Compatibility

The default behavior targets documented deepmerge 4.3.1 semantics. The suite
includes 5,000 deterministic differential cases. Intentional differences are
unsafe-key handling, cycle preservation, traversal limits, early option
validation, and modern package exports.

## Canonical links

Documentation: https://alexandro.net/docs/vanilla/deepmerge/
npm: https://www.npmjs.com/package/@stackline/deepmerge
Repository: https://github.com/alexandroit/stackline-deepmerge
Security: https://github.com/alexandroit/stackline-deepmerge/security/policy