pt/Reference/Global_Objects/Function/caller) Non-standard  Deprecated 
    3. [ ` Function: displayName ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/displayName) Non-standard 
    4. [ ` Function: length ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/length)
    5. [ ` Function: name ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/name)
    6. [ ` Function: prototype ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/prototype)
  9. Methods 
    1. [ ` Function.prototype[@@hasInstance]() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/@@hasInstance)
    2. [ ` Function.prototype.apply() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply)
    3. [ ` Function.prototype.bind() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind)
    4. [ ` Function.prototype.call() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call)
    5. [ ` Function.prototype.toString() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/toString)
  10. [ ` Object ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)
  11. Properties 
    1. [ ` Object.prototype.constructor ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/constructor)
    2. [ ` Object.prototype.__proto__ ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/proto) Deprecated 
  12. Methods 
    1. [ ` Object.prototype.__defineGetter__() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineGetter__) Deprecated 
    2. [ ` Object.prototype.__defineSetter__() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__defineSetter__) Deprecated 
    3. [ ` Object.prototype.__lookupGetter__() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupGetter__) Deprecated 
    4. [ ` Object.prototype.__lookupSetter__() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/__lookupSetter__) Deprecated 
    5. [ ` Object.prototype.hasOwnProperty() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty)
    6. [ ` Object.prototype.isPrototypeOf() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf)
    7. [ ` Object.prototype.propertyIsEnumerable() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable)
    8. [ ` Object.prototype.toLocaleString() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toLocaleString)
    9. [ ` Object.prototype.toString() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/toString)
    10. [ ` Object.prototype.valueOf() ` ](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/valueOf)

##  In this article

  * Description 
  * Constructor 
  * Instance properties 
  * Instance methods 
  * Examples 
  * Specifications 
  * Browser compatibility 
  * See also 

#  FinalizationRegistry

A **` FinalizationRegistry ` ** object lets you request a callback when a
value is garbage-collected.

##  Description

` FinalizationRegistry ` provides a way to request that a _cleanup callback_
get called at some point when a value registered with the registry has been
_reclaimed_ (garbage-collected). (Cleanup callbacks are sometimes called
_finalizers_ .)

**Note:** Cleanup callbacks should not be used for essential program logic.
See  Notes on cleanup callbacks  for details.

You create the registry passing in the callback:

js

    
    
    const registry = new FinalizationRegistry((heldValue) => {
      // â¦
    });
    

Then you register any value you want a cleanup callback for by calling the `
register ` method, passing in the value and a _held value_ for it:

js

    
    
    registry.register(target, "some value");
    

The registry does not keep a strong reference to the value, as that would
defeat the purpose (if the registry held it strongly, the value would never be
reclaimed). In JavaScript, objects and [ non-registered symbols ](/en-