fast-copy
Advanced tools
Package description
The fast-copy npm package is a deep copying utility designed to be faster than other deep copy alternatives. It can handle various JavaScript data types and structures, including objects, arrays, dates, and more, providing a deep clone without the performance overhead of other libraries.
Deep copying objects
This feature allows you to create a deep copy of an object, ensuring that nested objects are also cloned rather than just their references.
const copy = require('fast-copy').default;
const original = { a: 1, b: { c: 2 } };
const cloned = copy(original);Deep copying arrays
Similar to objects, this feature enables deep copying of arrays, including nested arrays.
const copy = require('fast-copy').default;
const original = [1, 2, [3, 4]];
const cloned = copy(original);Copying other types
fast-copy can also clone other JavaScript types such as Date objects and regular expressions.
const copy = require('fast-copy').default;
const date = new Date();
const regex = new RegExp('ab+c', 'i');
const clonedDate = copy(date);
const clonedRegex = copy(regex);Lodash's clonedeep method provides deep cloning functionality. It is part of the larger Lodash library, which is a general utility library. Compared to fast-copy, lodash.clonedeep may be slower but is part of a well-established utility library with a wide range of functions.
The clone package offers deep cloning of objects and arrays. It is less focused on performance compared to fast-copy and does not handle some of the more complex data types that fast-copy can.
Deep-copy is another package that provides deep cloning capabilities. It is similar to fast-copy in its purpose but may not have the same performance optimizations.
The rfdc (Really Fast Deep Clone) package is a competitor to fast-copy, focusing on performance for deep cloning. It claims to be faster than other deep cloning libraries for certain use cases and is a good alternative to consider when performance is critical.
Readme
A blazing fast deep object copier
import copy from "fast-copy";
import { deepEqual } from "fast-equals";
const object = {
array: [123, { deep: "value" }],
map: new Map([["foo", {}], [{ bar: "baz" }, "quz"]])
};
const copiedObject = copy(object);
console.log(copiedObject === object); // false
console.log(deepEqual(copiedObject, object)); // true
Starting in 2.0.0, you can use the isStrict option to copy the object based on strict standards, meaning:
Array object) are copiedThis is significantly slower, so you should only use this if you believe it necessary.
console.log(copy(object, { isStrict: true }));
NOTE: This option is also aliased as copy.strict.
console.log(copy.strict(object));
Under the hood, fast-copy uses instanceof to determine object types, which can cause false negatives when used in combination with iframe-based objects. To handle this edge case, you can pass the realm in options, which identifies which realm the object comes from and will use that realm to drive both comparisons and constructors for the copies.
<iframe srcdoc="<script>var arr = ['foo', 'bar'];</script>"></iframe>
const iframe = document.querySelector("iframe");
const arr = iframe.contentWindow.arr;
console.log(copy(arr, { realm: iframe.contentWindow })); // ['foo', 'bar']
The following object types are deeply cloned when they are either properties on the object passed, or the object itself:
ArrayArrayBufferBlobBufferDataViewDateFloat32ArrayFloat64ArrayInt8ArrayInt16ArrayInt32ArrayMapObjectRegExpSetUint8ArrayUint8ClampedArrayUint16ArrayUint32ArrayReact componentsThe following object types are copied directly, as they are either primitives, cannot be cloned, or the common use-case implementation does not expect cloning:
AsyncFunctionBooleanErrorFunctionGeneratorFunctionNumberNullPromiseStringSymbolUndefinedWeakMapWeakSetCircular objects are supported out of the box as well. By default a cache based on WeakSet is used, but if WeakSet is not available then a standard Object fallback is used. The benchmarks quoted below are based on use of WeakSet.
Small number of properties, all values are primitives
| Operations / second | |
|---|---|
| fast-copy | 2,692,822 |
| clone | 1,420,277 |
| lodash.cloneDeep | 1,277,213 |
| fast-deepclone | 768,982 |
| ramda | 719,948 |
| fast-clone | 567,342 |
| deepclone | 509,547 |
| fast-copy (strict) | 420,804 |
Large number of properties, values are a combination of primitives and complex objects
| Operations / second | |
|---|---|
| fast-copy | 109,352 |
| fast-deepclone | 101,808 |
| ramda | 93,103 |
| deepclone | 74,270 |
| fast-clone | 49,911 |
| clone | 46,355 |
| lodash.cloneDeep | 43,900 |
| fast-copy (strict) | 33,440 |
Very large number of properties with high amount of nesting, mainly objects and arrays
| Operations / second | |
|---|---|
| fast-copy | 123 |
| fast-deepclone | 101 |
| fast-clone | 93 |
| lodash.cloneDeep | 92 |
| deepclone | 66 |
| clone | 50 |
| fast-copy (strict) | 42 |
| ramda | 5 |
Objects that deeply reference themselves
| Operations / second | |
|---|---|
| fast-copy | 1,143,074 |
| ramda | 750,430 |
| clone | 722,632 |
| lodash.cloneDeep | 580,005 |
| deepclone | 490,824 |
| fast-deepclone | 446,585 |
| fast-copy (strict) | 321,678 |
| fast-clone (not supported) | 0 |
Custom constructors, React components, etc
| Operations / second | |
|---|---|
| fast-copy | 78,422 |
| clone | 52,165 |
| lodash.cloneDeep | 39,648 |
| ramda | 32,372 |
| fast-deepclone | 27,518 |
| fast-clone | 27,495 |
| deepclone | 16,552 |
| fast-copy (strict) | 12,509 |
Standard practice, clone the repo and yarn (or npm i) to get the dependencies. The following npm scripts are available:
rolluprimraf on the dist folderbuild and build:minified scriptssrc folder (also runs on dev script)lint script, but with auto-fixerlint, test:coverage, and dist scriptsprepublishOnly and release with new versionprepublishOnly and release with new beta versionprepublishOnly and simulate a new releasedevtest foldertest with code coverage calculation via nyctest but keep persistent watcherFAQs
A blazing fast deep object copier
We found that fast-copy demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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