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https://github.com/stdlib-js/string-first
Return the first visual character(s) of a string.
https://github.com/stdlib-js/string-first
char character first javascript node node-js nodejs stdlib str string util utilities utility utils
Last synced: about 19 hours ago
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Return the first visual character(s) of a string.
- Host: GitHub
- URL: https://github.com/stdlib-js/string-first
- Owner: stdlib-js
- License: apache-2.0
- Created: 2023-06-02T12:40:26.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2024-09-01T06:37:19.000Z (about 1 month ago)
- Last Synced: 2024-09-01T08:06:17.226Z (about 1 month ago)
- Topics: char, character, first, javascript, node, node-js, nodejs, stdlib, str, string, util, utilities, utility, utils
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 1.24 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
Awesome Lists containing this project
README
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!
# first
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Return the first character(s) of a string.
## Installation
```bash
npm install @stdlib/string-first
```
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 first = require( '@stdlib/string-first' );
```
#### first( str\[, n]\[, options] )
Returns the first character(s) of a string.
```javascript
var out = first( 'last man standing' );
// returns 'l'
out = first( 'Hidden Treasures' );
// returns 'H'
```
The function supports the following options:
- **mode**: type of characters to return. Must be one of the following:
- `'grapheme'`: grapheme clusters. Appropriate for strings containing visual characters which can span multiple Unicode code points (e.g., emoji).
- `'code_point'`: Unicode code points. Appropriate for strings containing visual characters which are comprised of more than one Unicode code unit (e.g., ideographic symbols and punctuation and mathematical alphanumerics).
- `'code_unit'`: UTF-16 code units. Appropriate for strings containing visual characters drawn from the basic multilingual plane (BMP) (e.g., common characters, such as those from the Latin, Greek, and Cyrillic alphabets).
Default: `'grapheme'`.
By default, the function returns the first character. To return the first `n` characters, provide a second argument specifying the number of characters to return.
```javascript
var out = first( 'foo bar', 5 );
// returns 'foo b'
out = first( 'foo bar', 10 );
// returns 'foo bar'
```
## Notes
- By default, the function assumes the general case in which an input string may contain an arbitrary number of grapheme clusters. This assumption comes with a performance cost. Accordingly, if an input string is known to only contain visual characters of a particular type (e.g., only alphanumeric), one can achieve better performance by specifying the appropriate `mode` option.
## Examples
```javascript
var first = require( '@stdlib/string-first' );
var str = first( 'last man standing' );
// returns 'l'
str = first( 'presidential election' );
// returns 'p'
str = first( 'javaScript' );
// returns 'j'
str = first( 'Hidden Treasures' );
// returns 'H'
str = first( 'The Last of the Mohicans', 5 );
// returns 'The L'
str = first( '🐶🐮🐷🐰🐸', 2 );
// returns '🐶🐮'
str = first( '🐶🐮🐷🐰🐸', 10 );
// returns '🐶🐮🐷🐰🐸'
```
* * *
## CLI
## Installation
To use as a general utility, install the CLI package globally
```bash
npm install -g @stdlib/string-first-cli
```
### Usage
```text
Usage: first [options] []
Options:
-h, --help Print this message.
-V, --version Print the package version.
--n num Number of characters to return. Default: 1.
--split sep Delimiter for stdin data. Default: '/\\r?\\n/'.
--mode mode Type of character to return. Default: 'grapheme'.
```
### Notes
- If the split separator is a [regular expression][mdn-regexp], ensure that the `split` option is either properly escaped or enclosed in quotes.
```bash
# Not escaped...
$ echo -n $'beep\nboop' | first --split /\r?\n/
# Escaped...
$ echo -n $'beep\nboop' | first --split /\\r?\\n/
```
- The implementation ignores trailing delimiters.
### Examples
```bash
$ first beep
b
```
To use as a [standard stream][standard-streams],
```bash
$ echo -n 'beep\nboop' | first --n=2
be
bo
```
By default, when used as a [standard stream][standard-streams], the implementation assumes newline-delimited data. To specify an alternative delimiter, set the `split` option.
```bash
$ echo -n 'beep\tboop' | first --split '\t'
b
b
```
* * *
## See Also
- [`@stdlib/string-remove-first`][@stdlib/string/remove-first]: remove the first character(s) of a string.
- [`@stdlib/string-last`][@stdlib/string/last]: return the last character(s) of a string.
* * *
## 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/string-first.svg
[npm-url]: https://npmjs.org/package/@stdlib/string-first
[test-image]: https://github.com/stdlib-js/string-first/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/string-first/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/string-first/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/string-first?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
[cli-section]: https://github.com/stdlib-js/string-first#cli
[cli-url]: https://github.com/stdlib-js/string-first/tree/cli
[@stdlib/string-first]: https://github.com/stdlib-js/string-first/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/string-first/tree/deno
[deno-readme]: https://github.com/stdlib-js/string-first/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/string-first/tree/umd
[umd-readme]: https://github.com/stdlib-js/string-first/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/string-first/tree/esm
[esm-readme]: https://github.com/stdlib-js/string-first/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/string-first/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/string-first/main/LICENSE
[standard-streams]: https://en.wikipedia.org/wiki/Standard_streams
[mdn-regexp]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Regular_Expressions
[@stdlib/string/remove-first]: https://github.com/stdlib-js/string-remove-first
[@stdlib/string/last]: https://github.com/stdlib-js/string-last