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https://github.com/stdlib-js/utils-unshift
Add one or more elements to the beginning of a collection.
https://github.com/stdlib-js/utils-unshift
append array extend float32array float64array int32array javascript lengthen node node-js nodejs stdlib typed-array uint32array unshift util utilities utility utils
Last synced: about 18 hours ago
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Add one or more elements to the beginning of a collection.
- Host: GitHub
- URL: https://github.com/stdlib-js/utils-unshift
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-15T18:47:25.000Z (over 3 years ago)
- Default Branch: main
- Last Pushed: 2024-10-01T11:53:07.000Z (2 days ago)
- Last Synced: 2024-10-01T23:04:43.983Z (1 day ago)
- Topics: append, array, extend, float32array, float64array, int32array, javascript, lengthen, node, node-js, nodejs, stdlib, typed-array, uint32array, unshift, util, utilities, utility, utils
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 1.39 MB
- Stars: 2
- Watchers: 3
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Citation: CITATION.cff
- Security: SECURITY.md
Awesome Lists containing this project
README
About stdlib...
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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!
# unshift
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Add one or more elements to the beginning of a collection.
## Installation
```bash
npm install @stdlib/utils-unshift
```
Alternatively,
- To load the package in a website via a `script` tag without installation and bundlers, use the [ES Module][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).
- If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).
- For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).
The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.
To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.
## Usage
```javascript
var unshift = require( '@stdlib/utils-unshift' );
```
#### unshift( collection, ...items )
Adds one or more elements to the beginning of a `collection`. A `collection` may be either an [`Array`][mdn-array], [`Typed Array`][mdn-typed-array], or an array-like [`Object`][mdn-object] (i.e., an [`Object`][mdn-object] having a valid writable `length` property).
```javascript
var arr = [ 1.0, 2.0, 3.0, 4.0, 5.0 ];
var out = unshift( arr, 6.0, 7.0 );
// returns [ 6.0, 7.0, 1.0, 2.0, 3.0, 4.0, 5.0 ]
var bool = ( out === arr );
// returns true
```
In contrast to [`Array.prototype.unshift`][mdn-array-unshift], the function returns the extended collection, rather than the collection length. For [typed arrays][mdn-typed-array], the returned value is a new [typed array][mdn-typed-array] view whose underlying [`ArrayBuffer`][mdn-arraybuffer] may **not** equal the underlying [`ArrayBuffer`][mdn-arraybuffer] for the input `collection`.
```javascript
var ArrayBuffer = require( '@stdlib/array-buffer' );
var Float64Array = require( '@stdlib/array-float64' );
var buf = new ArrayBuffer( 3*8 ); // 8 bytes per double
var arr = new Float64Array( buf, 8, 2 );
arr[ 0 ] = 1.0;
arr[ 1 ] = 2.0;
var out = unshift( arr, 3.0 );
// returns [ 3.0, 1.0, 2.0 ]
var bool = ( out === arr );
// returns false
bool = ( out.buffer === arr.buffer );
// returns true
out = unshift( out, 4.0 );
// returns [ 4.0, 3.0, 1.0, 2.0 ]
bool = ( out.buffer === arr.buffer );
// returns false
```
## Notes
- The function adds one or more elements to a [typed array][mdn-typed-array] by setting values in the underlying [`ArrayBuffer`][mdn-arraybuffer]. If an [`ArrayBuffer`][mdn-arraybuffer] does not have enough bytes in which to store all elements, the function allocates a new [`ArrayBuffer`][mdn-arraybuffer] capable of holding `2^n` elements, where `n` is the next power of `2`. This procedure is similar to how environments internally handle dynamic memory allocation for [`Arrays`][mdn-array].
- Beware when providing [typed arrays][mdn-typed-array] which are views pointing to a shared (or pooled) [`ArrayBuffer`][mdn-arraybuffer]. Because the function sets [`ArrayBuffer`][mdn-arraybuffer] bytes outside of a provided [view][mdn-typed-array], the function may overwrite bytes belonging to one or more external views. This could be a potential **security vulnerability**. Prefer providing [typed arrays][mdn-typed-array] which have an exclusive [`ArrayBuffer`][mdn-arraybuffer]; otherwise, be sure to plan for and guard against mutated state.
## Examples
```javascript
var Float64Array = require( '@stdlib/array-float64' );
var unshift = require( '@stdlib/utils-unshift' );
var arr;
var i;
arr = new Float64Array();
for ( i = 0; i < 100; i++ ) {
arr = unshift( arr, i );
}
console.log( arr );
```
* * *
## See Also
- [`@stdlib/utils-pop`][@stdlib/utils/pop]: remove and return the last element of a collection.
- [`@stdlib/utils-push`][@stdlib/utils/push]: add one or more elements to the end of a collection.
- [`@stdlib/utils-shift`][@stdlib/utils/shift]: remove and return the first element of a collection.
* * *
## 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].
[npm-image]: http://img.shields.io/npm/v/@stdlib/utils-unshift.svg
[npm-url]: https://npmjs.org/package/@stdlib/utils-unshift
[test-image]: https://github.com/stdlib-js/utils-unshift/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/utils-unshift/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/utils-unshift/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/utils-unshift?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-unshift/tree/deno
[deno-readme]: https://github.com/stdlib-js/utils-unshift/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/utils-unshift/tree/umd
[umd-readme]: https://github.com/stdlib-js/utils-unshift/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/utils-unshift/tree/esm
[esm-readme]: https://github.com/stdlib-js/utils-unshift/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/utils-unshift/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/utils-unshift/main/LICENSE
[mdn-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array
[mdn-array-unshift]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/unshift
[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Typed_arrays
[mdn-arraybuffer]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer
[mdn-object]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object
[@stdlib/utils/pop]: https://github.com/stdlib-js/utils-pop
[@stdlib/utils/push]: https://github.com/stdlib-js/utils-push
[@stdlib/utils/shift]: https://github.com/stdlib-js/utils-shift