Test if a string starts with the characters of another string.
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> Test if a string starts with the characters of another string.
``bash`
npm install @stdlib/string-starts-with
`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
`
- 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.position
- The function does not clamp negative values. Instead, when provided a negative position, the function resolves the starting search position relative to the end of the string.search
- Except when provided an empty string, the function always returns false if a position resolves to a starting search position which exceeds the bounds of the input string.
`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
`
- [@stdlib/string-starts-with-cli][@stdlib/string-starts-with-cli]: CLI package for use as a command-line utility.
- [@stdlib/string-ends-with][@stdlib/string/ends-with]: test if a string ends with the characters of another string.
*
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].
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---
See [LICENSE][stdlib-license].
Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
[@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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[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://www.npmjs.com/package/@stdlib/string-ends-with