@stdlib/utils-copy
TypeScript icon, indicating that this package has built-in type declarations

0.2.1 • Public • Published
About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

Copy

NPM version Build Status Coverage Status

Copy or deep clone a value to an arbitrary depth.

Installation

npm install @stdlib/utils-copy

Usage

var copy = require( '@stdlib/utils-copy' );

copy( value[, level] )

Copy or deep clone an input value to an arbitrary depth. The function accepts both objects and primitives.

// Primitives...
var out = copy( 'beep' );
// returns 'beep'

// Objects...
var value = [
    {
        'a': 1,
        'b': true,
        'c': [ 1, 2, 3 ]
    }
];
out = copy( value );
// returns [ { 'a': 1, 'b': true, 'c': [ 1, 2, 3 ] } ]

var bool = ( value[0].c === out[0].c );
// returns false

// Error object...
var err1 = new TypeError( 'beep' );

var err2 = copy( err1 );
// returns <TypeError>

The default behavior returns a full deep copy of any object. To limit the copy depth, set the level option.

var value = [
    {
        'a': 1,
        'b': true,
        'c': [ 1, 2, 3 ]
    }
];

// Trivial case => return the same reference
var out = copy( value, 0 );
// returns [ { 'a': 1, 'b': true, 'c': [ 1, 2, 3 ] } ]

var bool = ( value[0] === out[0] );
// returns true

// Shallow copy:
out = copy( value, 1 );

bool = ( value === out );
// returns false

bool = ( value[0] === out[0] );
// returns true

// Deep copy:
out = copy( value, 2 );

bool = ( value[0] === out[0] );
// returns false

bool = ( value[0].c === out[0].c );
// returns true

Notes

  • List of supported values/types:

  • List of unsupported values/types:

    • DOMElement: to copy DOM elements, use element.cloneNode().
    • Symbol
    • WeakMap
    • WeakSet
    • Blob
    • File
    • FileList
    • ImageData
    • ImageBitmap
    • ArrayBuffer
  • The implementation can handle circular references.

  • If a Number, String, or Boolean object is encountered, the value is cloned as a primitive. This behavior is intentional. The implementation is opinionated in wanting to avoid creating numbers, strings, and booleans via the new operator and a constructor.

  • For objects, the implementation only copies enumerable keys and their associated property descriptors.

  • The implementation only checks whether basic Objects, Arrays, and class instances are extensible, sealed, and/or frozen.

  • functions are not cloned; their reference is copied.

  • The implementation supports custom error types which are Error instances (e.g., ES2015 subclasses).

  • Support for copying class instances is inherently fragile. Any instances with privileged access to variables (e.g., within closures) cannot be cloned. This stated, basic copying of class instances is supported. Provided an environment which supports ES5, the implementation is greedy and performs a deep clone of any arbitrary class instance and its properties. The implementation assumes that the concept of level applies only to the class instance reference, but not to its internal state.

    function Foo() {
        this._data = [ 1, 2, 3, 4 ];
        this._name = 'bar';
        return this;
    }
    
    var foo1 = new Foo();
    var foo2 = copy( foo1 );
    
    var bool = ( foo1._name === foo2._name );
    // returns true
    
    bool = ( foo1._data === foo2._data );
    // returns false
    
    bool = ( foo1._data[0] === foo2._data[0] );
    // returns true

Examples

var randu = require( '@stdlib/random-base-randu' );
var Int32Array = require( '@stdlib/array-int32' );
var copy = require( '@stdlib/utils-copy' );

var arr = [
    {
        'x': new Date(),
        'y': [ randu(), randu() ],
        'z': new Int32Array( [ 1, 2, 3, 4 ] ),
        'label': 'Beep'
    },
    {
        'x': new Date(),
        'y': [ randu(), randu() ],
        'z': new Int32Array( [ 3, 1, 2, 4 ] ),
        'label': 'Boop'
    }
];

// Perform a full deep copy:
var out = copy( arr );

var bool = ( arr[ 0 ] === out[ 0 ] );
// returns false

bool = ( arr[ 1 ].y === out[ 1 ].y );
// returns false

// Perform a shallow copy:
out = copy( arr, 1 );

bool = ( arr[ 0 ] === out[ 0 ] );
// returns true

bool = ( arr[ 1 ].z === out[ 1 ].z );
// returns true

See Also


Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

Chat


License

See LICENSE.

Copyright

Copyright © 2016-2024. The Stdlib Authors.

Package Sidebar

Install

npm i @stdlib/utils-copy

Homepage

stdlib.io

Weekly Downloads

39,625

Version

0.2.1

License

Apache-2.0

Unpacked Size

66 kB

Total Files

13

Last publish

Collaborators

  • stdlib-bot
  • kgryte
  • planeshifter
  • rreusser