null-prototype-object

> A minimal utility for creating objects with a null prototype using a reusable constructor.

!Last version

Why not just Object.create(null)

Object.create(null) gives you a clean object with no prototype — useful for:

- Safe key-value maps
- Avoiding inherited methods (toString, hasOwnProperty, etc.)
- Preventing prototype pollution

But there's a performance cost in high-frequency scenarios.

$3

Each call to Object.create(null) creates a new object shape (hidden class).

JavaScript engines like V8 can't optimize repeated use because:

- The prototype isn't shared
- Shapes can't be reused
- Inline caching and JIT optimizations break down
- It leads to megamorphic call sites (a de-optimization trigger)

$3

This package provides a constructor with a frozen, shared null-prototype, enabling V8 to:

- Reuse a stable hidden class
- Inline property access
- Optimize memory layout
- Avoid dynamic shape transitions

$3

| Feature | Object.create(null) | new NullProtoObj() |
|---------------------------|------------------------|------------------------|
| Shared prototype | ❌ | ✅ |
| Hidden class reuse | ❌ | ✅ |
| Inline caching | ❌ | ✅ |
| JIT-friendly | ❌ | ✅ |
| Memory efficient | ❌ | ✅ |

$3

Use null-prototype-object if:

- You're allocating many null-prototype objects (e.g. parsers, serializers, caches).
- You want predictable performance in tight loops.
- You're optimizing object creation in hot code paths.

Install

``bash
$ npm install null-prototype-object --save
`

Usage

`js
const NullProtoObj = require('null-prototype-object')

const obj = new NullProtoObj()

// No inherited methods
console.log(obj.toString) // undefined

// Safe for dictionary-style use
obj.__proto__ = 'polluted? nope'
console.log(obj.__proto__) // => "polluted? nope"

console.log(obj.foo)
obj.foo = 'bar'
console.log(Object.getPrototypeOf(obj)) // ==> null (via prototype chain)
`

Benchmark

`
NullProtoObj via constructor x 207,586,282 ops/sec ±4.80% (81 runs sampled)
Object.create(null) x 54,415,324 ops/sec ±2.01% (89 runs sampled)
{} (normal object) x 194,340,713 ops/sec ±5.15% (77 runs sampled)
{__proto__:null} x 39,313,923 ops/sec ±2.37% (92 runs sampled)

Fastest is NullProtoObj via constructor
``

License

null-prototype-object © Kiko Beats, released under the MIT License.

Credits to pi0 and anonrig. Maintained by Kiko Beats with help from contributors.

> kikobeats.com · GitHub Kiko Beats · Twitter @kikobeats