@httpx/plain-object

Fast and lightweight (~80B) functions to check or assert that a value is a plain object.

A plain object is a basic JavaScript object, such as {}, { data: [] }, new Object() or Object.create(null).

See how it compares to other libraries.

Install

$ npm install @httpx/plain-object
$ yarn add @httpx/plain-object
$ pnpm add @httpx/plain-object

Features

• 👉  Provide isPlainObject and assertPlainObject functions.
• 🦄  Convenience PlainObject typescript typings.
• 🚀  Faster than most alternatives, see benchmarks.
• 📐  Lightweight (starts at ~80B)
• 🛡️  Tested on node 20-25, bun, browser, cloudflare workers and runtime/edge.
• 🙏  Works cross-realms (node:vm runInNewContext,...)
• 🗝️  Available in ESM and CJS formats.

Documentation

👉 Official website or GitHub Readme

Usage

isPlainObject

import { isPlainObject } from "@httpx/plain-object";

// ✅👇 True
isPlainObject({}); // ✅
isPlainObject({ key: "value" }); // ✅
isPlainObject({ key: new Date() }); // ✅
isPlainObject(new Object()); // ✅
isPlainObject(Object.create(null)); // ✅
isPlainObject({ nested: { key: true } }); // ✅
isPlainObject(new Proxy({}, {})); // ✅
isPlainObject({ [Symbol("tag")]: "A" }); // ✅

// ✅👇 (node context, workers, ...)
const runInNewContext = await import("node:vm").then(
  (mod) => mod.runInNewContext
);
isPlainObject(runInNewContext("({})")); // ✅

// ❌👇 False

class Test {}
isPlainObject(new Test()); // ❌
isPlainObject(10); // ❌
isPlainObject(null); // ❌
isPlainObject("hello"); // ❌
isPlainObject([]); // ❌
isPlainObject(new Date()); // ❌
isPlainObject(new Uint8Array([1])); // ❌
isPlainObject(Buffer.from("ABC")); // ❌
isPlainObject(Promise.resolve({})); // ❌
isPlainObject(Object.create({})); // ❌
isPlainObject(new (class Cls {})()); // ❌

// ⚠️ Edge cases
//
// 👇 globalThis isn't properly portable across all JS environments
//    In Bun, globalThis is a plain object, but in other environments
//    (browser, Nodejs, edge, cloudflare, deno), it's not.
//
// 👇 process.env isn't properly portable across all JS environments
//    In Bun && cloudlfare, process.env is a plain object, but in other environments
//    (browser, Nodejs, edge, cloudflare, deno), it's not.

isPlainObject(globalThis);          // ✅ with Bun ❌ otherwise (browser, Nodejs, edge, cloudflare, deno)
isPlainObject(process.env);         // ✅ with Bun and cloudflare ❌ otherwise (Nodejs, edge, deno)

// 👇 Static built-in classes aren't properly checked. This is a trade-off
//    to maintain the best performance and size. If you need to check for these,
//    use a custom type guard. But in most cases, you won't need to check for these
//    as the probability of writing a code that receives these as plain objects is low.
//    and probably indicates an issue in your code.

isPlainObject(Math); // ⚠️✅ return true, but Math is not a plain object
isPlainObject(JSON); // ⚠️✅ return true, but JSON is not a plain object
isPlainObject(Atomics); // ⚠️✅ return true, but Atomics is not a plain object
isPlainObject(Reflect); // ⚠️✅ return true, but Reflect is not a plain object

assertPlainObject

import { assertPlainObject } from "@httpx/plain-object";
import type { PlainObject } from "@httpx/plain-object";

function fn(value: unknown) {
  // 👇 Throws `new TypeError('Not a PlainObject')` if not a plain object
  assertPlainObject(value);

  // 👇 Throws `new TypeError('Custom message')` if not a plain object
  assertPlainObject(value, "Custom message");

  // 👇 Throws custom error if not a plain object
  assertPlainObject(value, () => {
    throw new HttpBadRequest("Custom message");
  });

  return value;
}

try {
  const value = fn({ key: "value" });
  // ✅ Value is known to be PlainObject<unknown>
  assertType<PlainObject>(value);
} catch (error) {
  console.error(error);
}

PlainObject type

Generic

ìsPlainObject and assertPlainObject accepts a generic to provide type autocompletion. Be aware that no runtime check are done. If you're looking for runtime validation, check zod, valibot or other alternatives.

import { isPlainObject } from "@httpx/plain-object";
import type { PlainObject } from "@httpx/plain-object";

type CustomType = {
  id: number;
  data?: {
    test: string[];
    attributes?: {
      url?: string | null;
      caption?: string | null;
      alternativeText?: string | null;
    } | null;
  } | null;
};

const value = { id: 1 } as unknown;

if (isPlainObject<CustomType>(value)) {
  // ✅ Value is a PlainObject with typescript autocompletion
  // Note that there's no runtime checking of keys, so they are
  // `unknown | undefined`. They will require unsing `?.` to access.

  const url = value?.data?.attributes?.url; // autocompletion works
  // ✅ url is `unknown | undefined`, so in order to use it, you'll need to
  //    manually check for the type.
  if (typeof url === "string") {
    console.log(url.toUpperCase());
  }
}

PlainObject

import { assertPlainObject } from "@httpx/plain-object";
import type { PlainObject } from "@httpx/plain-object";

function someFn(value: PlainObject) {
  //
}

const value = { key: "value" } as unknown;
assertPlainObject(value);
someFn(value);

Benchmarks

Performance is continuously monitored thanks to codspeed.io.

NodeJs 24.x

 RUN  v4.1.5 /home/sebastien/github/httpx/packages/plain-object


 ✓ bench/comparative.bench.ts > Compare calling isPlainObject with 110x mixed types values 7424ms
     name                                                           hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · "@httpx/plain-object": `isPlainObject(v)`            1,267,258.73  0.0007  0.8912  0.0008  0.0007  0.0015  0.0018  0.0102  ±0.67%   633631
   · "is-plain-obj":"4.1.0": 'isPlainObj(v)'              1,167,969.53  0.0007  2.5366  0.0009  0.0007  0.0015  0.0018  0.0104  ±1.27%   583985
   · "@sindresorhus/is":"8.0.0": 'is.plainObject(v)'      1,176,458.30  0.0007  0.7647  0.0009  0.0007  0.0014  0.0018  0.0130  ±0.77%   588230
   · "zod":"4.4.3": 'zod.util.isPlainObject(v)'             997,663.61  0.0008  1.8923  0.0010  0.0009  0.0017  0.0022  0.0143  ±1.08%   498832
   · "es-toolkit":"1.46.1": 'isPlainObject(v)'            1,040,376.28  0.0008  0.5971  0.0010  0.0008  0.0020  0.0022  0.0155  ±0.67%   520189
   · "redux":"5.0.1": 'isPlainObject(v)'                    406,199.96  0.0020  1.0312  0.0025  0.0021  0.0052  0.0061  0.0251  ±0.82%   203116
   · "is-plain-object":"5.0.0": 'isPlainObject(v)'          583,263.88  0.0014  4.1774  0.0017  0.0015  0.0035  0.0040  0.0207  ±1.81%   291632
   · "immer/is-plain-object":"4.2.0": 'isPlainObject(v)'    477,915.74  0.0019  0.6726  0.0021  0.0019  0.0038  0.0050  0.0208  ±0.62%   238958
   · lodash-es:"4.18.1": '_.isPlainObject(v)'                16,747.84  0.0467  1.8359  0.0597  0.0646  0.1725  0.2622  0.5797  ±1.46%     8375

 BENCH  Summary
                                                                                                                                                                                    
  "@httpx/plain-object": `isPlainObject(v)` - bench/comparative.bench.ts > Compare calling isPlainObject with 110x mixed types values
    1.08x faster than "@sindresorhus/is":"8.0.0": 'is.plainObject(v)'
    1.09x faster than "is-plain-obj":"4.1.0": 'isPlainObj(v)'
    1.22x faster than "es-toolkit":"1.46.1": 'isPlainObject(v)'
    1.27x faster than "zod":"4.4.3": 'zod.util.isPlainObject(v)'
    2.17x faster than "is-plain-object":"5.0.0": 'isPlainObject(v)'
    2.65x faster than "immer/is-plain-object":"4.2.0": 'isPlainObject(v)'
    3.12x faster than "redux":"5.0.1": 'isPlainObject(v)'
    75.67x faster than lodash-es:"4.18.1": '_.isPlainObject(v)'

Bun 1.3.13

Benchmarking is an experimental feature.
Breaking changes might not follow SemVer, please pin Vitest's version when using it.                                                                                                

 RUN  v4.1.5 /home/sebastien/github/httpx/packages/plain-object


 ✓ bench/comparative.bench.ts > Compare calling isPlainObject with 110x mixed types values 8270ms
     name                                                           hz     min     max    mean     p75     p99    p995    p999     rme  samples
   · "@httpx/plain-object": `isPlainObject(v)`            3,035,494.74  0.0002  2.0300  0.0003  0.0003  0.0006  0.0007  0.0018  ±0.98%  1517748
   · "is-plain-obj":"4.1.0": 'isPlainObj(v)'              2,910,611.34  0.0003  0.9960  0.0003  0.0003  0.0006  0.0007  0.0019  ±0.86%  1455306
   · "@sindresorhus/is":"8.0.0": 'is.plainObject(v)'      3,195,461.39  0.0003  1.8672  0.0003  0.0003  0.0006  0.0007  0.0017  ±1.15%  1597731
   · "zod":"4.4.3": 'zod.util.isPlainObject(v)'           1,158,960.66  0.0008  0.5257  0.0009  0.0008  0.0016  0.0020  0.0052  ±0.46%   579481
   · "es-toolkit":"1.46.1": 'isPlainObject(v)'            1,096,506.16  0.0008  1.5147  0.0009  0.0008  0.0016  0.0020  0.0102  ±0.80%   548254
   · "redux":"5.0.1": 'isPlainObject(v)'                  1,357,176.37  0.0005  2.1069  0.0007  0.0006  0.0013  0.0015  0.0067  ±1.31%   678589
   · "is-plain-object":"5.0.0": 'isPlainObject(v)'          567,347.42  0.0014  4.8731  0.0018  0.0015  0.0036  0.0043  0.0184  ±3.94%   283674
   · "immer/is-plain-object":"4.2.0": 'isPlainObject(v)'  1,607,338.90  0.0005  1.3589  0.0006  0.0006  0.0011  0.0014  0.0058  ±0.92%   803670
   · lodash-es:"4.18.1": '_.isPlainObject(v)'                40,471.25  0.0073  2.2837  0.0247  0.0289  0.1214  0.1528  0.3628  ±1.82%    20236

 BENCH  Summary
                                                                                                                                                                                    
  "@sindresorhus/is":"8.0.0": 'is.plainObject(v)' - bench/comparative.bench.ts > Compare calling isPlainObject with 110x mixed types values
    1.05x faster than "@httpx/plain-object": `isPlainObject(v)`
    1.10x faster than "is-plain-obj":"4.1.0": 'isPlainObj(v)'
    1.99x faster than "immer/is-plain-object":"4.2.0": 'isPlainObject(v)'
    2.35x faster than "redux":"5.0.1": 'isPlainObject(v)'
    2.76x faster than "zod":"4.4.3": 'zod.util.isPlainObject(v)'
    2.91x faster than "es-toolkit":"1.46.1": 'isPlainObject(v)'
    5.63x faster than "is-plain-object":"5.0.0": 'isPlainObject(v)'
    78.96x faster than lodash-es:"4.18.1": '_.isPlainObject(v)'

See benchmark file for details.

Bundle size

Bundle size is tracked by a size-limit configuration

| Scenario (esm) | Size (compressed) | | -------------------------------------------------------- | ----------------: | | import { isPlainObject } from '@httpx/plain-object | ~ 80B | | import { assertPlainObject } from '@httpx/plain-object | ~ 133B | | Both isPlainObject and assertPlainObject | ~ 141B |

For CJS usage (not recommended) track the size on bundlephobia.

Compatibility

| Level | CI | Description | | ------------ | --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Node | ✅ | CI for 20.x, 22.x, 24.x & 25.x. | | Browser | ✅ | Tested with latest chrome (vitest/playwright) | | Browserslist | ✅ | > 95% on 01/2025. defaults, chrome >= 96, firefox >= 105, edge >= 113, safari >= 15, ios >= 15, opera >= 103, not dead | | Bun | ✅ | Tested with latest (at time of writing >= 1.3.3) | | Edge | ✅ | Ensured on CI with @vercel/edge-runtime. | | Cloudflare | ✅ | Ensured with @cloudflare/vitest-pool-workers (see wrangler.toml | | Typescript | ✅ | TS 5.0 + / are-the-type-wrong checks on CI. | | ES2022 | ✅ | Dist files checked with es-check | | Performance | ✅ | Monitored with codspeed.io |

For older browsers: most frontend frameworks can transpile the library (ie: nextjs...)

Comparison with other libraries

| Library | Compat | Perf | CJS+ESM | | ---------------------------------------------------------------------- | ----------- | ------------- | ------- | | is-plain-obj | Differences | 1.17x slower | No | | es-toolkit | No | 1.25x slower | Yes | | (@redux)isPlainObject | ✅ 100% | 2.76x slower | Yes | | (lodash)isPlainObject | No | 83.50x slower | No |

redux/isPlainObject

100% compatible see tests.

@sindresorhus/is-plain-obj

This library wouldn't be possible without @sindresorhus is-plain-obj. Notable differences:

• [x] Slightly faster (10%) and lighter
• [x] ESM and CJS formats.
• [x] Named export.
• [x] Smaller bundle size.
• [x] Provide a PlainObject type and assertPlainObject function.
• [x] Typescript convenience PlainObject type.

Since v2, it diverges from is-plain-obj by

• [x] Static built-in classes are considered as plain objects (use isStaticBuiltInClass to exclude).
• [x] [Symbol.iterator] is considered as a valid property for plain objects.
• [x] [Symbol.toStringTag] is considered as a valid property for plain objects.`

Contributors

Contributions are welcome. Have a look to the CONTRIBUTING document.

Sponsors

If my OSS work brightens your day, let's take it to new heights together! Sponsor, coffee, or star – any gesture of support fuels my passion to improve. Thanks for being awesome! 🙏❤️

Special thanks to

License

MIT © Sébastien Vanvelthem and contributors.