https://github.com/stdlib-js/iter-head
Create an iterator which returns the first `n` values of a provided iterator.
https://github.com/stdlib-js/iter-head
first head iterable iterate iterator javascript node node-js nodejs peek stdlib take util utilities utility utils
Last synced: 15 days ago
JSON representation
Create an iterator which returns the first `n` values of a provided iterator.
- Host: GitHub
- URL: https://github.com/stdlib-js/iter-head
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-14T17:04:28.000Z (almost 4 years ago)
- Default Branch: main
- Last Pushed: 2024-12-09T02:49:21.000Z (6 months ago)
- Last Synced: 2025-05-03T17:44:15.638Z (28 days ago)
- Topics: first, head, iterable, iterate, iterator, javascript, node, node-js, nodejs, peek, stdlib, take, util, utilities, utility, utils
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 1.04 MB
- Stars: 1
- 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
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README
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# iterHead
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Create an [iterator][mdn-iterator-protocol] which returns the first `n` values of a provided [iterator][mdn-iterator-protocol].
## Installation
```bash
npm install @stdlib/iter-head
```
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 iterHead = require( '@stdlib/iter-head' );
```
#### iterHead( iterator, n )
Returns an [iterator][mdn-iterator-protocol] which returns the first `n` values of a provided [`iterator`][mdn-iterator-protocol].
```javascript
var array2iterator = require( '@stdlib/array-to-iterator' );
var it = iterHead( array2iterator( [ 1, 2, 3, 4 ] ), 2 );
// returns
var v = it.next().value;
// returns 1
v = it.next().value;
// returns 2
var bool = it.next().done;
// returns true
```
The returned [iterator][mdn-iterator-protocol] protocol-compliant object has the following properties:
- **next**: function which returns an [iterator][mdn-iterator-protocol] protocol-compliant object containing the next iterated value (if one exists) assigned to a `value` property and a `done` property having a `boolean` value indicating whether the [iterator][mdn-iterator-protocol] is finished.
- **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.
## Notes
- If a provided [iterator][mdn-iterator-protocol] only generates `m` values and `m` is less than `n`, the returned [iterator][mdn-iterator-protocol] only returns `m` values.
- If an environment supports `Symbol.iterator` **and** a provided [iterator][mdn-iterator-protocol] is iterable, the returned [iterator][mdn-iterator-protocol] is iterable.
## Examples
```javascript
var randu = require( '@stdlib/random-iter-randu' );
var iterHead = require( '@stdlib/iter-head' );
// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
'seed': 1234
});
// Create an iterator which returns the first 10 generated numbers:
var it = iterHead( rand, 10 );
// Perform manual iteration...
var r;
while ( true ) {
r = it.next();
if ( r.done ) {
break;
}
console.log( r.value );
}
```
* * *
## See Also
- [`@stdlib/iter-first`][@stdlib/iter/first]: return the first iterated value.
- [`@stdlib/iter-slice`][@stdlib/iter/slice]: create an iterator which returns a subsequence of iterated values from a provided iterator.
* * *
## 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/iter-head.svg
[npm-url]: https://npmjs.org/package/@stdlib/iter-head
[test-image]: https://github.com/stdlib-js/iter-head/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/iter-head/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/iter-head/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/iter-head?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/iter-head/tree/deno
[deno-readme]: https://github.com/stdlib-js/iter-head/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/iter-head/tree/umd
[umd-readme]: https://github.com/stdlib-js/iter-head/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/iter-head/tree/esm
[esm-readme]: https://github.com/stdlib-js/iter-head/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/iter-head/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/iter-head/main/LICENSE
[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol
[@stdlib/iter/first]: https://github.com/stdlib-js/iter-first
[@stdlib/iter/slice]: https://github.com/stdlib-js/iter-slice