@stdlib/utils-copy

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We greatly appreciate your continued support!</p> </details> # Copy [![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]  > Copy or deep clone a value to an arbitrary depth. <section class="installation"> ## Installation ```bash npm install @stdlib/utils-copy ``` </section> <section class="usage"> ## Usage ```javascript 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`. ```javascript // 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. ```javascript 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 ``` </section>  <section class="notes"> ## Notes - List of **supported** values/types: - `undefined` - `null` - `boolean`/`Boolean` - `string`/`String` - `number`/`Number` - `function` - `Object` - `Date` - `RegExp` - `Set` - `Map` - [`Error`][mdn-error] - [`URIError`][mdn-uri-error] - [`ReferenceError`][mdn-reference-error] - [`SyntaxError`][mdn-syntax-error] - [`RangeError`][mdn-range-error] - [`EvalError`][mdn-eval-error] - [`TypeError`][mdn-type-error] - [`System Error`][node-system-error] (Node.js) - `Array` - `Int8Array` - `Uint8Array` - `Uint8ClampedArray` - `Init16Array` - `Uint16Array` - `Int32Array` - `Uint32Array` - `Float32Array` - `Float64Array` - `Buffer` ([Node.js][node-buffer]) - 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`][mdn-error] types which are [`Error`][mdn-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.  ```javascript 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 ``` </section>  <section class="examples"> ## Examples  ```javascript 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 ``` </section>   <section class="related"> * * * ## See Also - <span class="package-name">[`@stdlib/utils-merge`][@stdlib/utils/merge]</span><span class="delimiter">: </span><span class="description">merge and extend objects.</span> </section>   <section class="main-repo" > * * * ## Notice This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib]. #### Community [![Chat][chat-image]][chat-url] --- ## License See [LICENSE][stdlib-license]. ## Copyright Copyright © 2016-2024. The Stdlib [Authors][stdlib-authors]. </section>   <section class="links"> [npm-image]: http://img.shields.io/npm/v/@stdlib/utils-copy.svg [npm-url]: https://npmjs.org/package/@stdlib/utils-copy [test-image]: https://github.com/stdlib-js/utils-copy/actions/workflows/test.yml/badge.svg?branch=v0.2.2 [test-url]: https://github.com/stdlib-js/utils-copy/actions/workflows/test.yml?query=branch:v0.2.2 [coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-copy/main.svg [coverage-url]: https://codecov.io/github/stdlib-js/utils-copy?branch=main  [chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg [chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im [stdlib]: https://github.com/stdlib-js/stdlib [stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors [umd]: https://github.com/umdjs/umd [es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules [deno-url]: https://github.com/stdlib-js/utils-copy/tree/deno [deno-readme]: https://github.com/stdlib-js/utils-copy/blob/deno/README.md [umd-url]: https://github.com/stdlib-js/utils-copy/tree/umd [umd-readme]: https://github.com/stdlib-js/utils-copy/blob/umd/README.md [esm-url]: https://github.com/stdlib-js/utils-copy/tree/esm [esm-readme]: https://github.com/stdlib-js/utils-copy/blob/esm/README.md [branches-url]: https://github.com/stdlib-js/utils-copy/blob/main/branches.md [stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-copy/main/LICENSE [mdn-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error [mdn-type-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError [mdn-syntax-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError [mdn-range-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RangeError [mdn-reference-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ReferenceError [mdn-uri-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/URIError [mdn-eval-error]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/EvalError [node-system-error]: https://nodejs.org/api/errors.html#errors_class_system_error [node-buffer]: http://nodejs.org/api/buffer.html  [@stdlib/utils/merge]: https://www.npmjs.com/package/@stdlib/utils-merge  </section>