FinalizationRegistry

`FinalizationRegistry.prototype.unregister`

Unregisters a target object from the FinalizationRegistry using the unregister token provided during registration

Syntax

JavaScript

registry.unregister(unregisterToken)

Parameters

Parameter	Type	Description
unregisterToken	object	The token previously passed as the third argument to register()

Return Value

A boolean: true if a registration was found and removed, false otherwise

Examples

Basic Usage

const registry = new FinalizationRegistry(() => console.log('collected'))
const obj = {}
const token = {}
registry.register(obj, 'value', token)
registry.unregister(token)

Practical Example

class ManagedResource {
  private registry = new FinalizationRegistry<string>(key => console.log(`GC: ${key}`))
  private tokens = new Map<string, object>()
  track(key: string, obj: object) {
    const token = {}
    this.tokens.set(key, token)
    this.registry.register(obj, key, token)
  }
  release(key: string) {
    const token = this.tokens.get(key)
    if (token) {
      this.registry.unregister(token)
      this.tokens.delete(key)
    }
  }
}

Advanced Usage

const registry = new FinalizationRegistry((v: string) => console.log(v))
const token = {}
const target = {}
registry.register(target, 'hello', token)
console.log(registry.unregister(token)) // true
console.log(registry.unregister(token)) // false

Understanding FinalizationRegistry.prototype.unregister

The FinalizationRegistry.prototype.unregister method in JavaScript unregisters a target object from the FinalizationRegistry using the unregister token provided during registration. It belongs to the FinalizationRegistry object and is one of the most widely used methods for working with finalizationregistry values in modern JavaScript and TypeScript applications.

The method signature is registry.unregister(unregisterToken). It accepts 1 parameter: unregisterToken. When called, it returns a boolean: true if a registration was found and removed, false otherwise. Understanding when and how to use unregister() helps you write more expressive, readable code.

Common use cases for FinalizationRegistry.prototype.unregister include data transformation, input validation, API response processing, and building reusable utility functions. It works well alongside related methods like finalizationregistry-register, finalizationregistry-constructor, weakref-deref, enabling you to chain operations together for complex data manipulation pipelines.

Supported in Chrome 84+, Firefox 79+, Safari 14.1+, Edge 84+, Node.js 14.6+.