npm package: @stdlib/string-starts-with
Description: Test if a string starts with the characters of another string.
Author: The Stdlib Authors
Latest version: 0.2.3

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<details>
  <summary>
    About stdlib...
  </summary>
  <p>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.</p>
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</details>

# startsWith

[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] <!-- [![dependencies][dependencies-image]][dependencies-url] -->

> Test if a string starts with the characters of another string.

<section class="intro">

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/string-starts-with
```

</section>

<section class="usage">

## 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
```

</section>

<!-- /.usage -->

<section class="notes">

## 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.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```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
```

</section>

<!-- /.examples -->



<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

## See Also

-   <span class="package-name">[`@stdlib/string-starts-with-cli`][@stdlib/string-starts-with-cli]</span><span class="delimiter">: </span><span class="description">CLI package for use as a command-line utility.</span>
-   <span class="package-name">[`@stdlib/string-ends-with`][@stdlib/string/ends-with]</span><span class="delimiter">: </span><span class="description">test if a string ends with the characters of another string.</span>

</section>

<!-- /.related -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->


<section class="main-repo" >

* * *

## 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 &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

</section>

<!-- /.stdlib -->

<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="links">

[@stdlib/string-starts-with-cli]: https://www.npmjs.com/package/@stdlib/string-starts-with-cli

[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=v0.2.3
[test-url]: https://github.com/stdlib-js/string-starts-with/actions/workflows/test.yml?query=branch:v0.2.3

[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

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[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

<!-- <related-links> -->

[@stdlib/string/ends-with]: https://www.npmjs.com/package/@stdlib/string-ends-with

<!-- </related-links> -->

</section>

<!-- /.links -->