https://github.com/stdlib-js/string-starts-with
Test if a string starts with the characters of another string.
https://github.com/stdlib-js/string-starts-with
begin begins check javascript match node node-js nodejs search start starts stdlib str string test util utilities utility utils
Last synced: 4 months ago
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Test if a string starts with the characters of another string.
- Host: GitHub
- URL: https://github.com/stdlib-js/string-starts-with
- Owner: stdlib-js
- License: apache-2.0
- Created: 2021-06-14T13:30:38.000Z (about 5 years ago)
- Default Branch: main
- Last Pushed: 2026-02-07T23:59:03.000Z (5 months ago)
- Last Synced: 2026-02-22T01:07:38.457Z (4 months ago)
- Topics: begin, begins, check, javascript, match, node, node-js, nodejs, search, start, starts, stdlib, str, string, test, util, utilities, utility, utils
- Language: JavaScript
- Homepage: https://github.com/stdlib-js/stdlib
- Size: 1.16 MB
- Stars: 1
- 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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# startsWith
[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url]
> Test if a string starts with the characters of another string.
## Installation
```bash
npm install @stdlib/string-starts-with
```
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 startsWith = require( '@stdlib/string-starts-with' );
```
#### startsWith( str, search\[, position] )
Tests if a string starts with the characters of another string.
```javascript
var str = 'To be, or not to be, that is the question.';
var bool = startsWith( str, 'To be' );
// returns true
bool = startsWith( str, 'to be' );
// returns false
```
By default, the function searches from the beginning of the input string. To search from a different character index, provide a `position` value (zero-based). If provided a negative `position`, the start index is determined relative to the string end (i.e., `pos = str.length + position`).
```javascript
var str = 'Remember the story I used to tell you when you were a boy?';
var bool = startsWith( str, 'the story' );
// returns false
bool = startsWith( str, 'the story', 9 );
// returns true
bool = startsWith( str, 'you', -15 );
// returns true
```
If provided an empty `search` string, the function **always** returns `true`.
```javascript
var str = 'beep boop';
var bool = startsWith( str, '' );
// returns true
```
## Notes
- This function differs from [`String.prototype.startsWith`][mdn-string-startswith] in the following ways:
- The function requires string values for the first and second arguments and requires that the `position` argument be an integer value.
- The function does **not** clamp negative `position` values. Instead, when provided a negative `position`, the function resolves the starting search position relative to the end of the string.
- Except when provided an empty `search` string, the function **always** returns `false` if a `position` resolves to a starting search position which exceeds the bounds of the input string.
## Examples
```javascript
var startsWith = require( '@stdlib/string-starts-with' );
var str = 'Fair is foul, and foul is fair, hover through fog and filthy air';
var bool = startsWith( str, 'Fair' );
// returns true
bool = startsWith( str, 'fair' );
// returns false
bool = startsWith( str, 'foul', 8 );
// returns true
bool = startsWith( str, 'filthy', -10 );
// returns true
```
* * *
## CLI
## Installation
To use as a general utility, install the CLI package globally
```bash
npm install -g @stdlib/string-starts-with-cli
```
### Usage
```text
Usage: starts-with [options] --search= []
Options:
-h, --help Print this message.
-V, --version Print the package version.
--search string Search string.
--pos int Search position.
--split sep Delimiter for stdin data. Default: '/\\r?\\n/'.
```
### 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 $'Hello, World!\nBeep Boop Baz' | starts-with --search=Beep --split /\r?\n/
# Escaped...
$ echo -n $'Hello, World!\nBeep Boop Baz' | starts-with --search=Beep --split /\\r?\\n/
```
- The implementation ignores trailing delimiters.
### Examples
```bash
$ starts-with --search=be beep
true
```
To use as a [standard stream][standard-streams],
```bash
$ echo -n 'boop' | starts-with --search=bo
true
```
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 'Hello, World!\tBeep Boop' | starts-with --search=Beep --split '\t'
false
true
```
* * *
## See Also
- [`@stdlib/string-ends-with`][@stdlib/string/ends-with]: test if a string ends with the characters of another 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 © 2016-2026. The Stdlib [Authors][stdlib-authors].
[npm-image]: http://img.shields.io/npm/v/@stdlib/string-starts-with.svg
[npm-url]: https://npmjs.org/package/@stdlib/string-starts-with
[test-image]: https://github.com/stdlib-js/string-starts-with/actions/workflows/test.yml/badge.svg?branch=main
[test-url]: https://github.com/stdlib-js/string-starts-with/actions/workflows/test.yml?query=branch:main
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/string-starts-with/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/string-starts-with?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/string-starts-with#cli
[cli-url]: https://github.com/stdlib-js/string-starts-with/tree/cli
[@stdlib/string-starts-with]: https://github.com/stdlib-js/string-starts-with/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-starts-with/tree/deno
[deno-readme]: https://github.com/stdlib-js/string-starts-with/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/string-starts-with/tree/umd
[umd-readme]: https://github.com/stdlib-js/string-starts-with/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/string-starts-with/tree/esm
[esm-readme]: https://github.com/stdlib-js/string-starts-with/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/string-starts-with/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/string-starts-with/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
[mdn-string-startswith]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/startsWith
[@stdlib/string/ends-with]: https://github.com/stdlib-js/string-ends-with