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Really Fast Deep Clone

Version published
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791 bytes
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Package description

What is rfdc?

The rfdc (Really Fast Deep Clone) npm package is a module that provides a very fast deep cloning function for copying complex data structures in JavaScript. It is optimized for performance and can handle various types of data including objects, arrays, dates, and more.

What are rfdc's main functionalities?

Deep cloning objects

This feature allows you to create a deep clone of an object, meaning that all nested objects and arrays are also recursively cloned.

{"const rfdc = require('rfdc')();
const obj = { a: 1, b: { c: 2 } };
const clone = rfdc(obj);
console.log(clone); // { a: 1, b: { c: 2 } }"}

Deep cloning arrays

This feature allows you to create a deep clone of an array, including cloning all nested arrays and objects within it.

{"const rfdc = require('rfdc')();
const arr = [1, [2, 3], [4, 5]];
const clone = rfdc(arr);
console.log(clone); // [1, [2, 3], [4, 5]]"}

Customizing clone behavior

This feature allows you to customize the cloning behavior, such as whether to preserve the prototype chain or handle circular references.

{"const rfdc = require('rfdc')({ proto: false, circles: false });
const obj = { a: 1 };
obj.b = obj;
// Throws an error because 'circles: false' does not allow circular references.
const clone = rfdc(obj);"}

Other packages similar to rfdc




Really Fast Deep Clone

build status coverage js-standard-style


const clone = require('rfdc')()
clone({a: 1, b: {c: 2}}) // => {a: 1, b: {c: 2}}


require('rfdc')(opts = { proto: false, circles: false }) => clone(obj) => obj2

proto option

Copy prototype properties as well as own properties into the new object.

It's marginally faster to allow enumerable properties on the prototype to be copied into the cloned object (not onto it's prototype, directly onto the object).

To explain by way of code:

require('rfdc')({ proto: false })(Object.create({a: 1})) // => {}
require('rfdc')({ proto: true })(Object.create({a: 1})) // => {a: 1}

Setting proto to true will provide an additional 2% performance boost.

circles option

Keeping track of circular references will slow down performance with an additional 25% overhead. Even if an object doesn't have any circular references, the tracking overhead is the cost. By default if an object with a circular reference is passed to rfdc, it will throw (similar to how JSON.stringify
would throw).

Use the circles option to detect and preserve circular references in the object. If performance is important, try removing the circular reference from the object (set to undefined) and then add it back manually after cloning instead of using this option.

default import

It is also possible to directly import the clone function with all options set to their default:

const clone = require("rfdc/default")
clone({a: 1, b: {c: 2}}) // => {a: 1, b: {c: 2}}


rfdc clones all JSON types:

  • Object
  • Array
  • Number
  • String
  • null

With additional support for:

  • Date (copied)
  • undefined (copied)
  • Buffer (copied)
  • TypedArray (copied)
  • Map (copied)
  • Set (copied)
  • Function (referenced)
  • AsyncFunction (referenced)
  • GeneratorFunction (referenced)
  • arguments (copied to a normal object)

All other types have output values that match the output of JSON.parse(JSON.stringify(o)).

For instance:

const rfdc = require('rfdc')()
const err = Error()
err.code = 1
JSON.parse(JSON.stringify(e)) // {code: 1}
rfdc(e) // {code: 1}

JSON.parse(JSON.stringify({rx: /foo/})) // {rx: {}}
rfdc({rx: /foo/}) // {rx: {}}


npm run bench
benchDeepCopy*100: 671.675ms
benchLodashCloneDeep*100: 1.574s
benchCloneDeep*100: 936.792ms
benchFastCopy*100: 822.668ms
benchFastestJsonCopy*100: 363.898ms // See note below
benchPlainObjectClone*100: 556.635ms
benchNanoCopy*100: 770.234ms
benchRamdaClone*100: 2.695s
benchJsonParseJsonStringify*100: 2.290s // JSON.parse(JSON.stringify(obj))
benchRfdc*100: 412.818ms
benchRfdcProto*100: 424.076ms
benchRfdcCircles*100: 443.357ms
benchRfdcCirclesProto*100: 465.053ms

It is true that fastest-json-copy may be faster, BUT it has such huge limitations that it is rarely useful. For example, it treats things like Date and Map instances the same as empty {}. It can't handle circular references. plain-object-clone is also really limited in capability.


npm test
169 passing (342.514ms)


npm run cov
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
All files |      100 |      100 |      100 |      100 |                   |
 index.js |      100 |      100 |      100 |      100 |                   |

__proto__ own property copying

rfdc works the same way as Object.assign when it comes to copying ['__proto__'] (e.g. when an object has an own property key called 'proto'). It results in the target object prototype object being set per the value of the ['__proto__'] own property.

For detailed write-up on how a way to handle this security-wise see





Last updated on 19 Jan 2024

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