Deno and Node support for non-registered symbols in Weak{Map,Set,Ref} and FinalizationRegistry

[lionel-rowe]

Summary

Updated info about Deno and Node support for non-registered symbols as Weak{Map,Set} keys and as WeakRef/FinalizationRegistry targets.

I tested with the specified versions, but may well be supported by lower versions than these — not sure how important it is that the version specified is strictly the minimum requirement?

Test results and supporting details

function assert(cond) {
    if (!cond) throw '!'
}

const tests = {
    WeakMap() {
        const wm = new WeakMap()
        const key = Symbol()
        const val = { data: 1 }
        wm.set(key, val)
        assert(wm.get(key) === val)
    },
    WeakSet() {
        const ws = new WeakSet()
        const key = Symbol()
        ws.add(key)
        assert(ws.has(key))
    },
    WeakRef() {
        new WeakRef(Symbol())
    },
    FinalizationRegistry() {
        new FinalizationRegistry(() => {}).register(Symbol())
    },
}

for (const [name, test] of Object.entries(tests)) {
    try {
        test()
        console.info(`✅ ${name} supported`)
    } catch(e) {
        console.error(`❌ ${name} unsupported`, e.message)
    }
}

Related issues

N/A

[queengooborg]

Hey there, thank you for digging into this!

This is something that could definitely be added to the mdn-bcd-collector. Would you be down to turn your test code into custom tests and submit a PR to the collector? (Happy to help if needed!)

I tested with the specified versions, but may well be supported by lower versions than these — not sure how important it is that the version specified is strictly the minimum requirement?

The version_added field should always be the earliest version the feature was supported in, rather than just the earliest version tested. We do, however, have "range syntax" -- in other words, prepending a ≤ character to state the feature may have been supported earlier -- which is allowed for releases older than two years!

[lionel-rowe]

This is something that could definitely be added to the mdn-bcd-collector. Would you be down to turn your test code into custom tests and submit a PR to the collector? (Happy to help if needed!)

Done - PR here: openwebdocs/mdn-bcd-collector#1445

[lionel-rowe]

The version_added field should always be the earliest version the feature was supported in, rather than just the earliest version tested. We do, however, have "range syntax" -- in other words, prepending a ≤ character to state the feature may have been supported earlier -- which is allowed for releases older than two years!

I've updated these too now.

[queengooborg]

Thank you, this is looking good to me!