npm package: @stdlib/string-base-replace-before-last
Description: Replace the substring before the last occurrence of a specified search string.
Author: The Stdlib Authors
Latest version: 0.1.2

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    About stdlib...
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  <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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# replaceBeforeLast

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

> Replace the substring before the last occurrence of a specified search string.

<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->

<section class="intro">

</section>

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<!-- Package usage documentation. -->

<section class="installation">

## Installation

```bash
npm install @stdlib/string-base-replace-before-last
```

</section>

<section class="usage">

## Usage

```javascript
var replaceBeforeLast = require( '@stdlib/string-base-replace-before-last' );
```

#### replaceBeforeLast( str, search, replacement, fromIndex )

Replaces the substring before the last occurrence of a specified search string.

```javascript
var str = 'beep boop';
var out = replaceBeforeLast( str, ' ', 'loop', str.length );
// returns 'loop boop'

out = replaceBeforeLast( str, 'o', 'bar', str.length );
// returns 'barop'
```

To begin searching from a specific index, provide a corresponding `fromIndex` argument.

```javascript
var out = replaceBeforeLast( 'beep boop beep', ' ', 'loop', 5 );
// returns 'loop boop beep'
```

If `fromIndex` is less than zero, the starting index is resolved relative to the last string character, with the last string character corresponding to `fromIndex = -1`.

```javascript
var out = replaceBeforeLast( 'beep boop beep', ' ', 'loop', -1 );
// returns 'loop beep'
```

</section>

<!-- /.usage -->

<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

<section class="notes">

## Notes

-   If a search string is not present in a provided string, the function returns the provided string unchanged.
-   If a search string is an empty string, the function returns the provided string unchanged.
-   If `fromIndex` resolves to an index which is less than `0`, the function returns the provided string unchanged.

</section>

<!-- /.notes -->

<!-- Package usage examples. -->

<section class="examples">

## Examples

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

```javascript
var replaceBeforeLast = require( '@stdlib/string-base-replace-before-last' );

var str = 'beep boop';
var out = replaceBeforeLast( str, 'p', 'see', str.length );
// returns 'seep'

str = 'Hello World!';
out = replaceBeforeLast( str, 'xyz', 'foo', str.length );
// returns 'Hello World!'

str = 'Hello World!';
out = replaceBeforeLast( str, '', 'foo', str.length );
// returns 'Hello World!'

str = '';
out = replaceBeforeLast( str, 'xyz', 'foo', str.length );
// returns ''
```

</section>

<!-- /.examples -->

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</section>

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<section class="related">

* * *

## See Also

-   <span class="package-name">[`@stdlib/string-base/replace-after-last`][@stdlib/string/base/replace-after-last]</span><span class="delimiter">: </span><span class="description">replace the substring after the last occurrence of a specified search string.</span>
-   <span class="package-name">[`@stdlib/string-base/replace-after`][@stdlib/string/base/replace-after]</span><span class="delimiter">: </span><span class="description">replace the substring after the first occurrence of a specified search string.</span>
-   <span class="package-name">[`@stdlib/string-base/replace-before`][@stdlib/string/base/replace-before]</span><span class="delimiter">: </span><span class="description">replace the substring before the first occurrence of a specified search string.</span>

</section>

<!-- /.related -->

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<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>

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

[@stdlib/string/base/replace-after-last]: https://www.npmjs.com/package/@stdlib/string-base-replace-after-last

[@stdlib/string/base/replace-after]: https://www.npmjs.com/package/@stdlib/string-base-replace-after

[@stdlib/string/base/replace-before]: https://www.npmjs.com/package/@stdlib/string-base-replace-before

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</section>

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