null-prototype-object

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

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.

The problem

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)

The solution: null-prototype-object

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

Why it’s faster

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

When to use it

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

$ npm install null-prototype-object --save

Usage

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