96 lines
4.4 KiB
Markdown
96 lines
4.4 KiB
Markdown
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# structuredClone polyfill
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[](https://www.npmjs.com/package/@ungap/structured-clone) [](https://github.com/ungap/structured-clone/actions) [](https://coveralls.io/github/ungap/structured-clone?branch=main)
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An env agnostic serializer and deserializer with recursion ability and types beyond *JSON* from the *HTML* standard itself.
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* [Supported Types](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm#supported_types)
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* *not supported yet*: Blob, File, FileList, ImageBitmap, ImageData, and ArrayBuffer, but typed arrays are supported without major issues, but u/int8, u/int16, and u/int32 are the only safely suppored (right now).
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* *not possible to implement*: the `{transfer: []}` option can be passed but it's completely ignored.
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* [MDN Documentation](https://developer.mozilla.org/en-US/docs/Web/API/structuredClone)
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* [Serializer](https://html.spec.whatwg.org/multipage/structured-data.html#structuredserializeinternal)
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* [Deserializer](https://html.spec.whatwg.org/multipage/structured-data.html#structureddeserialize)
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Serialized values can be safely stringified as *JSON* too, and deserialization resurrect all values, even recursive, or more complex than what *JSON* allows.
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### Examples
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Check the [100% test coverage](./test/index.js) to know even more.
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```js
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// as default export
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import structuredClone from '@ungap/structured-clone';
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const cloned = structuredClone({any: 'serializable'});
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// as independent serializer/deserializer
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import {serialize, deserialize} from '@ungap/structured-clone';
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// the result can be stringified as JSON without issues
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// even if there is recursive data, bigint values,
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// typed arrays, and so on
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const serialized = serialize({any: 'serializable'});
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// the result will be a replica of the original object
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const deserialized = deserialize(serialized);
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```
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#### Global Polyfill
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Note: Only monkey patch the global if needed. This polyfill works just fine as an explicit import: `import structuredClone from "@ungap/structured-clone"`
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```js
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// Attach the polyfill as a Global function
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import structuredClone from "@ungap/structured-clone";
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if (!("structuredClone" in globalThis)) {
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globalThis.structuredClone = structuredClone;
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}
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// Or don't monkey patch
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import structuredClone from "@ungap/structured-clone"
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// Just use it in the file
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structuredClone()
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```
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**Note**: Do not attach this module's default export directly to the global scope, whithout a conditional guard to detect a native implementation. In environments where there is a native global implementation of `structuredClone()` already, assignment to the global object will result in an infinite loop when `globalThis.structuredClone()` is called. See the example above for a safe way to provide the polyfill globally in your project.
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### Extra Features
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There is no middle-ground between the structured clone algorithm and JSON:
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* JSON is more relaxed about incompatible values: it just ignores these
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* Structured clone is inflexible regarding incompatible values, yet it makes specialized instances impossible to reconstruct, plus it doesn't offer any helper, such as `toJSON()`, to make serialization possible, or better, with specific cases
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This module specialized `serialize` export offers, within the optional extra argument, a **lossy** property to avoid throwing when incompatible types are found down the road (function, symbol, ...), so that it is possible to send with less worrying about thrown errors.
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```js
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// as default export
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import structuredClone from '@ungap/structured-clone';
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const cloned = structuredClone(
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{
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method() {
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// ignored, won't be cloned
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},
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special: Symbol('also ignored')
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},
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{
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// avoid throwing
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lossy: true,
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// avoid throwing *and* looks for toJSON
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json: true
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}
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);
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```
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The behavior is the same found in *JSON* when it comes to *Array*, so that unsupported values will result as `null` placeholders instead.
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#### toJSON
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If `lossy` option is not enough, `json` will actually enforce `lossy` and also check for `toJSON` method when objects are parsed.
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Alternative, the `json` exports combines all features:
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```js
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import {stringify, parse} from '@ungap/structured-clone/json';
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parse(stringify({any: 'serializable'}));
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```
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