https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at
Test if a position in a string marks the start of a UTF-16 surrogate pair.
https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at
astral code javascript node node-js nodejs point pt stdlib str string surrogate unicode utf-16 utf16 util utilities utility utils
Last synced: about 1 month ago
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Test if a position in a string marks the start of a UTF-16 surrogate pair.
- Host: GitHub
- URL: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-14T16:55:05.000Z (almost 5 years ago)
- Default Branch: main
- Last Pushed: 2026-02-08T00:30:56.000Z (about 2 months ago)
- Last Synced: 2026-02-08T08:10:40.948Z (about 2 months ago)
- Topics: astral, code, javascript, node, node-js, nodejs, point, pt, stdlib, str, string, surrogate, unicode, utf-16, utf16, util, utilities, utility, utils
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 1.04 MB
- Stars: 2
- Watchers: 2
- 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
- Notice: NOTICE
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README
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# hasUTF16SurrogatePairAt
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Test if a position in a string marks the start of a [UTF-16][utf-16] surrogate pair.
## Installation
```bash
npm install @stdlib/assert-has-utf16-surrogate-pair-at
```
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]).
- To use as a general utility for the command line, install the corresponding [CLI package][cli-section] globally.
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 hasUTF16SurrogatePairAt = require( '@stdlib/assert-has-utf16-surrogate-pair-at' );
```
#### hasUTF16SurrogatePairAt( string, position )
Tests if a `position` (in [UTF-16][utf-16] code units) in a `string` marks the start of a [UTF-16][utf-16] surrogate pair.
```javascript
var bool = hasUTF16SurrogatePairAt( '🌷', 0 );
// returns true
bool = hasUTF16SurrogatePairAt( '🌷', 1 );
// returns false
```
## Notes
- Note that `position` does **not** refer to a visual character position, but to an index in the ordered sequence of [UTF-16][utf-16] code units.
## Examples
```javascript
var hasUTF16SurrogatePairAt = require( '@stdlib/assert-has-utf16-surrogate-pair-at' );
var bool = hasUTF16SurrogatePairAt( '🌷', 0 );
// returns true
bool = hasUTF16SurrogatePairAt( '🌷', 1 );
// returns false
```
* * *
## CLI
## Installation
To use as a general utility, install the CLI package globally
```bash
npm install -g @stdlib/assert-has-utf16-surrogate-pair-at-cli
```
### Usage
```text
Usage: has-utf16-surrogate-pair-at [options] [] --pos=
Options:
-h, --help Print this message.
-V, --version Print the package version.
--pos index Position in string.
```
### Examples
```bash
$ has-utf16-surrogate-pair-at --pos=0 🌷
true
```
To use as a [standard stream][standard-streams],
```bash
$ echo -n '🌷' | has-utf16-surrogate-pair-at --pos=1
false
```
* * *
## 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 © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/assert-has-utf16-surrogate-pair-at.svg
[npm-url]: https://npmjs.org/package/@stdlib/assert-has-utf16-surrogate-pair-at
[test-image]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/assert-has-utf16-surrogate-pair-at/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/assert-has-utf16-surrogate-pair-at?branch=main
[chat-image]: https://img.shields.io/badge/zulip-join_chat-brightgreen.svg
[chat-url]: https://stdlib.zulipchat.com
[stdlib]: https://github.com/stdlib-js/stdlib
[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors
[cli-section]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at#cli
[cli-url]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/tree/cli
[@stdlib/assert-has-utf16-surrogate-pair-at]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/tree/main
[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/assert-has-utf16-surrogate-pair-at/tree/deno
[deno-readme]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/tree/umd
[umd-readme]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/tree/esm
[esm-readme]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/assert-has-utf16-surrogate-pair-at/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/assert-has-utf16-surrogate-pair-at/main/LICENSE
[utf-16]: https://en.wikipedia.org/wiki/UTF-16
[standard-streams]: https://en.wikipedia.org/wiki/Standard_streams