Benchmark: lodash merge vs deepmerge vs deepmerge-ts vs @fastify/deepmerge vs just-extend (take 3)

HTML Preparation code:

<script src='https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js'></script>
<script src='https://unpkg.com/deepmerge@4.3.1/dist/umd.js'></script>
<script type="module">
import { deepmerge } from 'https://unpkg.com/deepmerge-ts@5.1.0/dist/node/index.mjs';
window.deepmergeTs = deepmerge;
</script>
<script type="module">
import extend from 'https://unpkg.com/just-extend@6.2.0/index.mjs';
window.justExtend = extend;
</script>
<script type="module">
// CJS only :(
// https://unpkg.com/browse/@fastify/deepmerge@1.3.0/
const JSON_PROTO = Object.getPrototypeOf({})

function deepmergeConstructor (options) {
  function isNotPrototypeKey (value) {
    return (
      value !== 'constructor' &&
      value !== 'prototype' &&
      value !== '__proto__'
    )
  }

  function cloneArray (value) {
    let i = 0
    const il = value.length
    const result = new Array(il)
    for (i = 0; i < il; ++i) {
      result[i] = clone(value[i])
    }
    return result
  }

  function cloneObject (target) {
    const result = {}

    if (cloneProtoObject && Object.getPrototypeOf(target) !== JSON_PROTO) {
      return cloneProtoObject(target)
    }

    const targetKeys = getKeys(target)
    let i, il, key
    for (i = 0, il = targetKeys.length; i < il; ++i) {
      isNotPrototypeKey(key = targetKeys[i]) &&
        (result[key] = clone(target[key]))
    }
    return result
  }

  function concatArrays (target, source) {
    const tl = target.length
    const sl = source.length
    let i = 0
    const result = new Array(tl + sl)
    for (i = 0; i < tl; ++i) {
      result[i] = clone(target[i])
    }
    for (i = 0; i < sl; ++i) {
      result[i + tl] = clone(source[i])
    }
    return result
  }

  const propertyIsEnumerable = Object.prototype.propertyIsEnumerable
  function getSymbolsAndKeys (value) {
    const result = Object.keys(value)
    const keys = Object.getOwnPropertySymbols(value)
    for (let i = 0, il = keys.length; i < il; ++i) {
      propertyIsEnumerable.call(value, keys[i]) && result.push(keys[i])
    }
    return result
  }

  const getKeys = options && options.symbols
    ? getSymbolsAndKeys
    : Object.keys

  const cloneProtoObject = typeof options?.cloneProtoObject === 'function'
    ? options.cloneProtoObject
    : undefined

  function isMergeableObject (value) {
    return typeof value === 'object' && value !== null && !(value instanceof RegExp) && !(value instanceof Date)
  }

  function isPrimitive (value) {
    return typeof value !== 'object' || value === null
  }

  const isPrimitiveOrBuiltIn = typeof Buffer !== 'undefined'
    ? (value) => typeof value !== 'object' || value === null || value instanceof RegExp || value instanceof Date || value instanceof Buffer
    : (value) => typeof value !== 'object' || value === null || value instanceof RegExp || value instanceof Date

  const mergeArray = options && typeof options.mergeArray === 'function'
    ? options.mergeArray({ clone, deepmerge: _deepmerge, getKeys, isMergeableObject })
    : concatArrays

  function clone (entry) {
    return isMergeableObject(entry)
      ? Array.isArray(entry)
        ? cloneArray(entry)
        : cloneObject(entry)
      : entry
  }

  function mergeObject (target, source) {
    const result = {}
    const targetKeys = getKeys(target)
    const sourceKeys = getKeys(source)
    let i, il, key
    for (i = 0, il = targetKeys.length; i < il; ++i) {
      isNotPrototypeKey(key = targetKeys[i]) &&
      (sourceKeys.indexOf(key) === -1) &&
      (result[key] = clone(target[key]))
    }

    for (i = 0, il = sourceKeys.length; i < il; ++i) {
      isNotPrototypeKey(key = sourceKeys[i]) &&
      (
        key in target && (targetKeys.indexOf(key) !== -1 && (result[key] = _deepmerge(target[key], source[key])), true) || // eslint-disable-line no-mixed-operators
        (result[key] = clone(source[key]))
      )
    }
    return result
  }

  function _deepmerge (target, source) {
    const sourceIsArray = Array.isArray(source)
    const targetIsArray = Array.isArray(target)

    if (isPrimitive(source)) {
      return source
    } else if (isPrimitiveOrBuiltIn(target)) {
      return clone(source)
    } else if (sourceIsArray && targetIsArray) {
      return mergeArray(target, source)
    } else if (sourceIsArray !== targetIsArray) {
      return clone(source)
    } else {
      return mergeObject(target, source)
    }
  }

  function _deepmergeAll () {
    switch (arguments.length) {
      case 0:
        return {}
      case 1:
        return clone(arguments[0])
      case 2:
        return _deepmerge(arguments[0], arguments[1])
    }
    let result
    for (let i = 0, il = arguments.length; i < il; ++i) {
      result = _deepmerge(result, arguments[i])
    }
    return result
  }

  return options && options.all
    ? _deepmergeAll
    : _deepmerge
}
window.deepmergeFastify = deepmergeConstructor
</script>

Script Preparation code:

const a = { a: 'oh', b: 'my', c: { a: 'a', b: { c: 'c' } } };
const b = { c: { b: { d: 'a'  }, c: { d: 'd' } } };
const c = {
    foo: { bar: 3 },
    array: [{
        does: 'work',
        too: [ 1, 2, 3 ]
    }]
}
const d = {
    foo: { baz: 4 },
    quux: 5,
    array: [{
        does: 'work',
        too: [ 4, 5, 6 ]
    }, {
        really: 'yes'
    }]
}
const objects = { a, b, c, d }
window.OBJECTS = objects;

Tests:

lodash merge
const one = _.merge({}, OBJECTS.a, OBJECTS.b); const two = _.merge({}, OBJECTS.c, OBJECTS.d);
deepmerge
const one = deepmerge({}, OBJECTS.a, OBJECTS.b); const two = deepmerge({}, OBJECTS.c, OBJECTS.d);
deepmerge-ts
const one = deepmergeTs({}, OBJECTS.a, OBJECTS.b); const two = deepmergeTs({}, OBJECTS.c, OBJECTS.d);
fastify deepmerge
const _merge = deepmergeFastify(); const one = deepmergeFastify({}, OBJECTS.a, OBJECTS.b); const two = deepmergeFastify({}, OBJECTS.c, OBJECTS.d);
fastify deepmerge, with 'all: true'
const _merge = deepmergeFastify({ all: true }); const one = _merge({}, OBJECTS.a, OBJECTS.b); const two = _merge({}, OBJECTS.c, OBJECTS.d);
just-extend
const one = justExtend(true, {}, OBJECTS.a, OBJECTS.b); const two = justExtend(true, {}, OBJECTS.c, OBJECTS.d);

Historical Performance Data aggregated from 12 community runs

Desktop Results:

Chrome 12 runs

fastify deepmerge

3.0M/s

fastify deepmerge, with 'all: true'

667K/s

deepmerge

655K/s

deepmerge-ts

248K/s

lodash merge

195K/s

just-extend

175K/s

Fastest: fastify deepmerge (16.9x faster)

View exact numbers

✓ fastify deepmerge: 2,969,090 ops/sec
• fastify deepmerge, with 'all: true': 666,774 ops/sec
• deepmerge: 654,614 ops/sec
• deepmerge-ts: 248,074 ops/sec
• lodash merge: 194,504 ops/sec
• just-extend: 175,206 ops/sec

Results show median performance across all community submissions. Run this benchmark yourself to verify on your device.

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
lodash merge
deepmerge
deepmerge-ts
fastify deepmerge
fastify deepmerge, with 'all: true'
just-extend

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 9 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/141.0.0.0 Safari/537.36 Edg/141.0.0.0

Browser/OS: Chrome 141 on Linux

View result in a separate tab

fastify deepmerge

2.0M/s

fastify deepmerge, with 'all: true'

441K/s

deepmerge

364K/s

deepmerge-ts

141K/s

just-extend

116K/s

lodash merge

112K/s

View exact numbers

Test name	Executions per second
✓ fastify deepmerge	2,043,241 Ops/sec
fastify deepmerge, with 'all: true'	441,418 Ops/sec
deepmerge	364,473 Ops/sec
deepmerge-ts	140,505 Ops/sec
just-extend	116,089 Ops/sec
lodash merge	111,799 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

lodash merge vs deepmerge vs deepmerge-ts vs @fastify/deepmerge vs just-extend (take 3) (version: 2)

Comparing performance of: `lodash merge vs deepmerge vs deepmerge-ts vs fastify deepmerge vs fastify deepmerge, with 'all: true' vs just-extend`

Created: 3 years ago by: Registered User

Go to the latest result

lodash merge

deepmerge

deepmerge-ts

fastify deepmerge

fastify deepmerge, with 'all: true'

just-extend

Historical Performance Data aggregated from 12 community runs

Desktop Results:

Chrome 12 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

lodash merge vs deepmerge vs deepmerge-ts vs @fastify/deepmerge vs just-extend (take 3) (version: 2)

Comparing performance of: lodash merge vs deepmerge vs deepmerge-ts vs fastify deepmerge vs fastify deepmerge, with 'all: true' vs just-extend

Created: 3 years ago by: Registered User

Go to the latest result

lodash merge

deepmerge

deepmerge-ts

fastify deepmerge

fastify deepmerge, with 'all: true'

just-extend

Historical Performance Data aggregated from 12 community runs

Desktop Results:

Chrome 12 runs

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

Related benchmarks

Comparing performance of: `lodash merge vs deepmerge vs deepmerge-ts vs fastify deepmerge vs fastify deepmerge, with 'all: true' vs just-extend`