JS Built-ins
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FinalizationRegistryregisterbeginner

FinalizationRegistry.register — unregister available

📖 Usage Example
const reg = new FinalizationRegistry(k => {})
let obj = {}
const token = {}
reg.register(obj, 'key', token)
reg.unregister(token)  // cancels the cleanup

Pass a third (token) argument to register() so you can later unregister before GC.

unregister After register

After creating a registry, typeof reg.unregister is 'function'.

Challenge: Verify unregister is available.

💡 Hints (1)
  • • unregister allows you to cancel a previously registered cleanup callback.