Backport structuredClone to Node v16

[fregante]

#39713 added structuredClone and it landed in v17

Is it possible to back port it to v16? It'd be great to see it in an LTS sooner rather than later

[lpinca]

#39759 was marked semver-major so no, it will not be backported unless an exception is made for this. I can't remember if there is a precedent for something like this.

cc: @aduh95 @nodejs/releasers

[MylesBorins]

If the Semver-Major bit is to add a new global we could potentially backport as a requireable / importable module

edit: confirmed major was due to global

[dinuvld]

Is there any update on when or if the feature would be backported?

Not waiting 2 years for another LTS release to get this would be amazing as it's such a useful addition. Currently adding lodash for the cloneDeep() functionality is a very bloated work-around.

[DerekNonGeneric]

Yeah, it would be nice to have, but we are still discovering problems with it almost weekly and still need to ensure that it is spec-compliant or at least matches expected behavior and having nothing yet specified in the ECMAScript specification for it means that we have to piece together behavior specified elsewhere, so really it should only be used in experimental (non-production) settings probably only for academic purposes at the moment. The current implementation will very likely change and I wouldn't consider the current behavior safe to use in some cases, so I'm surprised it even shipped so soon, but that's just my opinion (and not a very developed one at that, so I digress).

[richardlau]

Not waiting 2 years for another LTS release to get this would be amazing as it's such a useful addition.

We release new LTS lines every year. The next new LTS release (Node.js 18) is planned to become LTS in October this year.

[voxpelli]

What’s the best way to achieve identical functionality on Node 16?

Would you accept a PR for the suggestion from @MylesBorins of making it a requireable function?

Or would it be possible to extract this implementation and make it a third party polyfill on npm?

[aduh95]

What’s the best way to achieve identical functionality on Node 16? […] Or would it be possible to extract this implementation and make it a third party polyfill on npm?

I think making it an npm package is the easiest way to get it for Node.js 16.x. The original suggestion from Anna should Just Works™:

I think a drop-in structuredClone for Node.js could be:

{
  const { MessageChannel, receiveMessageOnPort } = require('worker_threads');
  const channel = new MessageChannel();
  channel.unref();
  globalThis.structuredClone = function structuredClone(value, transfer) {
    channel.port1.postMessage(value, transfer);
    return receiveMessageOnPort(channel.port2).message;
  }:
}

Source: #39713 (comment)

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