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isWeakMap

Checks whether a value is a WeakMap.

This helper performs a strict instanceof check and never throws or mutates input. It accepts native WeakMap instances, WeakMap subclasses, and wrapper objects created with Object(...).

Signature

function isWeakMap<K extends object = object, V = unknown>(
    value: unknown,
): value is WeakMap<K, V>

Parameters

Name Data type Description
value unknown The value to validate.
field string The name of the field being validated, used in error reporting.

Returns

A boolean:

  • true: If the value is a WeakMap.
  • false: Otherwise.

Examples

isWeakMap(new WeakMap())          // true
isWeakMap(Object(new WeakMap()))  // true

isWeakMap(new Map())              // false
isWeakMap({})                     // false
isWeakMap(null)                   // false

Notes

  • This helper intentionally accepts WeakMap wrapper objects because JavaScript treats them as genuine WeakMap instances.
  • It does not treat plain objects or Maps as WeakMaps.
  • Use validateWeakMap if you need a Result<T> instead of a boolean.