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Fauz Gabriel 32af5f6e7f base commit		2026-02-23 16:39:35 +07:00
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README.md

is-finalizationregistry

Is this value a JS FinalizationRegistry? This module works cross-realm/iframe, and despite ES6 @@toStringTag.

Example

var isFinalizationRegistry = require('is-finalizationregistry');
assert(!isFinalizationRegistry(function () {}));
assert(!isFinalizationRegistry(null));
assert(!isFinalizationRegistry(function* () { yield 42; return Infinity; });
assert(!isFinalizationRegistry(Symbol('foo')));
assert(!isFinalizationRegistry(1n));
assert(!isFinalizationRegistry(Object(1n)));

assert(!isFinalizationRegistry(new Set()));
assert(!isFinalizationRegistry(new WeakSet()));
assert(!isFinalizationRegistry(new Map()));
assert(!isFinalizationRegistry(new WeakMap()));
assert(!isFinalizationRegistry(new WeakRef({})));

assert(isFinalizationRegistry(new FinalizationRegistry(function () {})));

class MyFinalizationRegistry extends FinalizationRegistry {}
assert(isFinalizationRegistry(new MyFinalizationRegistry(function () {})));

Tests

Simply clone the repo, npm install, and run npm test