normalizePlainObject

Normalizes a plain-object-like value into a real plain object or returns null.

This helper accepts objects whose prototype is either Object.prototype or null. It rejects arrays, functions, class instances, and built-in exotic objects. It never throws and never mutates input.

Use this when you need to ensure that a value is a safe, JSON-like object before further processing or validation.

Signature

function normalizePlainObject(value: unknown): Record<string, unknown> | null

Parameters

Name	Data type	Description
value	unknown	The value to normalize into a plain object.

Returns

One of:

• A plain object — if the input is object-like and its prototype is Object.prototype or null.
• null: If the value cannot be interpreted as a plain object.

Behavior

• Accepts:
• Objects whose prototype is exactly Object.prototype.
• Objects created using Object.create(null) (null-prototype objects).
• Rejects:
• Arrays.
• Functions.
• Class instances.
• Built-in objects: Map, Set, Date, RegExp, Error, etc.
• Objects with custom prototypes.
• Objects whose prototype getter throws.
• All non-object values.

Uses Reflect.getPrototypeOf safely (wrapped in try/catch).

Examples

normalizePlainObject({ a: 1 })               
// { a: 1 }

const obj = Object.create(null)
obj.x = 1
normalizePlainObject(obj)                    
// { x: 1 }

normalizePlainObject([])                     
// null

normalizePlainObject(new Map())              
// null

normalizePlainObject(new (class Foo {})())   
// null

normalizePlainObject(123)                    
// null
normalizePlainObject("abc")                  
// null
normalizePlainObject(null)                   
// null

Notes

• Use normalizeRecord if you want to enforce that all keys are strings and all values are serializable.
• Use validatePlainObject if you need structured error information instead of returning null.
• Plain objects are useful for JSON-like data structures, but for deep validation consider chaining with validateObjectShape, schemas, or normalizers for nested values.