npm install is-weakrefyarn add is-weakrefpnpm add is-weakref<script src="https://fastly.jsdelivr.net/npm/is-weakref"></script><script src="https://unpkg.com/is-weakref"></script><script type="module">
import isweakref from 'https://cdn.jsdelivr.net/npm/is-weakref/+esm';
</script><script type="module">
import isweakref from 'https://cdn.skypack.dev/is-weakref';
</script>