offers foolproof deep cloning of objects, arrays, numbers, strings, maps, sets, promises, etc. in JavaScript.

npm install clone

(It also works with browserify, ender or standalone. You may want to use the option noParse in browserify to reduce the resulting file size, since usually Buffers are not needed in browsers.)

var clone = require('clone');

var a, b;

a = { foo: { bar: 'baz' } };  // initial value of a

b = clone(a);                 // clone a -> b
a.foo.bar = 'foo';            // change a

console.log(a);               // show a
console.log(b);               // show b

This will print:

{ foo: { bar: 'foo' } }
{ foo: { bar: 'baz' } }

clone masters cloning simple objects (even with custom prototype), arrays, Date objects, and RegExp objects. Everything is cloned recursively, so that you can clone dates in arrays in objects, for example.

• value: The value that you want to clone, any type allowed.
• circular: Boolean, defaults to true. Call clone with circular set to false if you are certain that obj contains no circular references. This will give better performance if needed. There is no error if undefined or null is passed as obj.
• depth: Depth to which the object is to be cloned (optional, defaults to Infinity)
• prototype: Sets the prototype to be used when cloning an Object. (optional, defaults to __proto__ of the to be cloned value, ie. the cloned object will have the same prototype as the original).
• includeNonEnumerable: Set to true if the non-enumerable properties should be cloned as well. Non-enumerable properties on the prototype chain will be ignored. (optional, defaults to false)

you can specify circular, depth, prototype and includeNonEnumerable with a single opts Object.

• obj -- the object that you want to clone

Does a prototype clone as described by Oran Looney.

var a, b;

a = { hello: 'world' };

a.myself = a;
b = clone(a);

console.log(b);

This will print:

{ hello: "world", myself: [Circular] }

So, b.myself points to b, not a. Neat!

npm test

• Use Buffer.allocUnsafe() on Node >= 4.5.0 (contributed by @ChALkeR)

• Fix build badge in README
• Add support for cloning Maps and Sets on Internet Explorer

• Add support for cloning Errors
• Exclude non-enumerable symbol-named object properties from cloning
• Add option to include non-enumerable own properties of objects

• Add support for cloning ES6 Maps, Sets, Promises, and Symbols

• Use Buffer.allocUnsafe() on Node >= 4.5.0 (contributed by @ChALkeR; backported from v2.1.2)

• Close XSS vulnerability in the NPM package, which included the file test-apart-ctx.html. This vulnerability was disclosed by Juho Nurminen of 2NS - Second Nature Security.

• Fix call on getRegExpFlags
• Refactor utilities
• Refactor test suite

• Fix nodeunit version
• Directly call getRegExpFlags

• Improve browser support
• Improve browser testability
• Move helper methods to private namespace

Some special objects like a socket or process.stdout/stderr are known to not be cloneable. If you find other objects that cannot be cloned, please open an issue.

If you encounter any bugs or issues, feel free to open an issue at github or send me an email to paul@vorba.ch. I also always like to hear from you, if you’re using my code.

Copyright © 2011-2016 Paul Vorbach and contributors.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.