is-weakmap

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

Usage no npm install needed!

<script type="module">
  import isWeakmap from 'https://cdn.skypack.dev/is-weakmap';
</script>

README

is-weakmap

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

Example

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

assert(!isWeakMap(new Set()));
assert(!isWeakMap(new WeakSet()));
assert(!isWeakMap(new Map()));

assert(isWeakMap(new WeakMap()));

class MyWeakMap extends WeakMap {}
assert(isWeakMap(new MyWeakMap()));

Tests

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