Return the part of a string before a specified substring.
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> Return the part of a string before a specified substring.
``bash`
npm install @stdlib/string-substring-before
`javascript`
var substringBefore = require( '@stdlib/string-substring-before' );
#### substringBefore( str, search )
Returns the part of a string before a specified substring.
`javascript
var str = 'beep boop';
var out = substringBefore( str, ' ' );
// returns 'beep'
out = substringBefore( str, 'o' );
// returns 'beep b'
`
- If a substring is not present in a provided string, the function returns the input string.
- If provided an empty substring, the function returns an empty string.
`javascript
var substringBefore = require( '@stdlib/string-substring-before' );
var out = substringBefore( 'beep boop', 'p' );
// returns 'bee'
out = substringBefore( 'Hello World!', 'xyz' );
// returns 'Hello World!'
out = substringBefore( 'Hello World!', '' );
// returns ''
out = substringBefore( '', 'xyz' );
// returns ''
`
- [@stdlib/string-substring-before-cli][@stdlib/string-substring-before-cli]: CLI package for use as a command-line utility.
- [@stdlib/string-substring-before-last][@stdlib/string/substring-before-last]: return the part of a string before the last occurrence of a specified substring.
- [@stdlib/string-substring-after][@stdlib/string/substring-after]: return the part of a string after a specified substring.
- [@stdlib/string-substring-after-last][@stdlib/string/substring-after-last]: return the part of a string after the last occurrence of a specified substring.
*
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-substring-before-cli]: https://www.npmjs.com/package/@stdlib/string-substring-before-cli
[npm-image]: http://img.shields.io/npm/v/@stdlib/string-substring-before.svg
[npm-url]: https://npmjs.org/package/@stdlib/string-substring-before
[test-image]: https://github.com/stdlib-js/string-substring-before/actions/workflows/test.yml/badge.svg?branch=v0.2.3
[test-url]: https://github.com/stdlib-js/string-substring-before/actions/workflows/test.yml?query=branch:v0.2.3
[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/string-substring-before/main.svg
[coverage-url]: https://codecov.io/github/stdlib-js/string-substring-before?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-substring-before#cli
[cli-url]: https://github.com/stdlib-js/string-substring-before/tree/cli
[@stdlib/string-substring-before]: https://github.com/stdlib-js/string-substring-before/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-substring-before/tree/deno
[deno-readme]: https://github.com/stdlib-js/string-substring-before/blob/deno/README.md
[umd-url]: https://github.com/stdlib-js/string-substring-before/tree/umd
[umd-readme]: https://github.com/stdlib-js/string-substring-before/blob/umd/README.md
[esm-url]: https://github.com/stdlib-js/string-substring-before/tree/esm
[esm-readme]: https://github.com/stdlib-js/string-substring-before/blob/esm/README.md
[branches-url]: https://github.com/stdlib-js/string-substring-before/blob/main/branches.md
[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/string-substring-before/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/substring-before-last]: https://www.npmjs.com/package/@stdlib/string-substring-before-last
[@stdlib/string/substring-after]: https://www.npmjs.com/package/@stdlib/string-substring-after
[@stdlib/string/substring-after-last]: https://www.npmjs.com/package/@stdlib/string-substring-after-last