Fastest JSON deep clone in JavaScript

[![deno land][deno-badge]][deno] [![npm][npm-badge]][npm] [![CI][ci-badge]][ci]
[![CC0 1.0][license-badge]][license]

This project is based on
fast-json-clone.

[fast-clone-json][npm] is a tiny library to clone [JSON][json] values in pure
JavaScript focusing on the speed. According to the benchmark, this
package seems the fastest among several deep-clone implementations.

``javascript
import * as assert from "assert";
import { cloneJson } from "fast-clone-json";

const value = {
str: "hello",
num: 42,
array: [true, null],
object: { str: "hello", bool: true },
};

const cloned = cloneJson(value);

assert.deepStrictEqual(value, cloned);
assert.notStrictEqual(value, cloned);
assert.notStrictEqual(value.array, cloned.array);
assert.notStrictEqual(value.object, cloned.object);
`

Installation

This package is licensed with CC0-1.0. Directly copy
src/clone.ts to your project.

Or install via npm package manager.

`sh
npm install --save fast-clone-json
`

API

This package exports cloneJson() and cloneJsonObject() functions.

`javascript
cloneJson(x: JsonValue): JsonValue;
`

This function clones the given JSON value and returns it. There are some
invariants for the parameter:

- The parameter must not contain circles as JSON does not allow it. This
function will cause infinite loop for such values by design.
- The parameter must contain JSON values only. Other values like Date,
Regexp, Map, Set, Buffer, ... are not allowed.

`javascript
cloneJsonObject(x: JsonObject): JsonObject;
`

This function clones the given JSON object and returns it. There are additional
invariants for the parameter:

- All invariants of cloneJson().
- Directly specified parameters must be arrays or objects. Primitive values such
as string cannot be specified.

Benchmark

Here is the benchmark result with large (1.2MB) JSON value. This package is the
fastest among the implementations. Please see the benchmark directory
for more details and other results.

!Performance large

`
Native structuredClone x 104 ops/sec ±0.40% (76 runs sampled)
structuredClone polyfill x 105 ops/sec ±0.59% (77 runs sampled)
JSON serialize/deserialize x 98.93 ops/sec ±0.69% (72 runs sampled)
Naive deep clone x 208 ops/sec ±0.18% (88 runs sampled)
lodash.clonedeep x 123 ops/sec ±2.42% (80 runs sampled)
clone-deep x 194 ops/sec ±0.38% (89 runs sampled)
rfdc (default) x 481 ops/sec ±0.19% (93 runs sampled)
rfdc (proto) x 551 ops/sec ±0.26% (92 runs sampled)
fastest-json-copy x 561 ops/sec ±0.15% (94 runs sampled)
fast-json-clone x 584 ops/sec ±0.15% (95 runs sampled)
fast-clone-json (cloneJson) x 591 ops/sec ±0.24% (95 runs sampled)
fast-clone-json (cloneJsonObject) x 592 ops/sec ±0.24% (93 runs sampled)

Fastest is fast-clone-json (cloneJsonObject),fast-clone-json (cloneJson)
`

FAQ

$3

Since this package is optimized for removing non-inline function calls in the
hot loop as much as possible. [rfdc][rfdc] is implemented with the same
strategy.

$3

Since this package provides less functionalities. rfdc provides support for some
non-JSON types (Date, Regexp`, ...). It increases the number of branches in
the hot loop so it causes trade-off in performance.

$3

You are right. Improvements in this package are minor. In some cases it may be
slower. (eg, differences in CPUs and Javascript engines.)

License

This package is distributed under [CC0 1.0][license] (Public Domain). Feel free
to copy and paste the implementation directly to your project without any
copyright notice.

[ci]: https://github.com/Milly/fast-clone-json/actions/workflows/ci.yml
[ci-badge]: https://github.com/Milly/fast-clone-json/actions/workflows/ci.yml/badge.svg
[deno]: https://deno.land/x/fast_clone_json
[deno-badge]: https://img.shields.io/badge/deno.land-x%2Ffast__clone__json-lightgrey?logo=deno
[npm]: https://www.npmjs.com/package/fast-clone-json
[npm-badge]: https://badge.fury.io/js/fast-clone-json.svg
[license]: https://github.com/Milly/fast-clone-json/blob/master/LICENSE
[license-badge]: https://img.shields.io/github/license/Milly/fast-clone-json
[json]: https://json.org/
[rfdc]: https://github.com/davidmarkclements/rfdc
[benchmark]: https://github.com/Milly/fast-clone-json/tree/master/bench#readme